


Haze

by Askellie



Category: Undertale (Video Game)
Genre: Attempted Rape/Non-Con, Blood and Injury, Canon-Typical Violence, Cross has never had a heat before, Crosstale Sans (Undertale), Crosstale Sans/Dreamtale Nightmare Sans (Undertale), Crosstale Sans/Dusttale Sans, Crosstale Sans/Errortale Sans, Crosstale Sans/Horrortale Sans, Dreamtale Nightmare Sans (Undertale), Dusttale Sans (Undertale), Errortale Sans (Undertale), Horrortale Sans (Undertale), Killer Sans (Undertale) - Freeform, Killer Sans/Crosstale Sans, M/M, Mating Cycles/In Heat, Oh no its a heat fic, Poor Crosstale Sans (Undertale), Sharing a Body, Undertale Multiverse, XChara - Freeform, he has no idea, oh no
Language: English
Status: In-Progress
Published: 2020-08-15
Updated: 2020-12-01
Packaged: 2021-03-05 21:07:00
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 6
Words: 25,040
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25911832
Author URL: https://archiveofourown.org/users/Askellie/pseuds/Askellie
Summary: That muddy, warm feeling in his bones? Cross is pretty sure it's just a fever. That throbbing, heavy feeling in his soul? Probably just Chara messing with him again. He's never felt this way before, but that doesn't mean it's anything to worry about.[Cross experiences heat for the first time. The rest of Nightmare's crew are as unhelpful as you would expect.]
Relationships: Cross/Dust, Cross/Horror, Crossmare, Killer / Cross, Kross - Relationship, Maybe Cross/Error too hmm, Nightmare/Cross, Sans/Sans (Undertale)
Comments: 199
Kudos: 603





	1. Chapter 1

Cross is used to snapping awake in an instant, his soul pounding with LOVE and the handle of a knife already half-materialised between his fingertips. He doesn’t dare to sleep often. Even now that Chara’s been convinced (threatened, bribed) not to steal control of his body again, their dual awareness means Cross’s mind never seems to be able to find peace. The moment he lets his guard down, the memories creep in; his and Chara’s, and sometimes other fragments that he doesn’t think belong to either of them.

The dusty tunnels of an empty underground.

Razor sharp wire traps clotted with the gore of escaped prey. 

Bright red blood all over his hands, the color so visceral his sockets burn like he’s staring into the sun.

And a felled tree, a strangely innocuous image for how gutted he feels after that particular dream, like everything in the world has been irreparably broken. 

He’s so used to dreaming of misery and death, of dust and blood and cracking bones and splintered wood, that he doesn’t even recognise what’s happening at first. Sleep lets him go with a gentle reluctance, leaving him blinking slowly at the ceiling, feeling languid and warm and appallingly comfortable. The magic between his bones is fizzling softly like bubbles in a can soda, a pressure that’s both excitable and anticipatory. For the first time he feels strangely disappointed that the tantalysing figments of his dream slips away from him before he can hold it in his memory, and it's not until he tries to move that he understands why.

“Hah…”

His pelvis gives a jarringly unexpected throb that tingles all the way up his spine, making his toes curl reflexively against the mattress. He’s suddenly uncomfortably aware of the coarse fabric of his shorts clinging to his bones, and the way that his undershirt has ridden up to his collarbones, tangling uncomfortably beneath his armpits. The cool air prickles at his exposed rib cage, which is rising and falling with heavy swells of breath. 

Wet dreams are the territory of clumsy adolescents, not of highly trained royal guards, but for a moment Cross feels his soul coiling tight with a pang of want. He can’t remember anything substantial about the dream, no names or faces to match the insufferable urgency to have another monster’s hands on him. There’s nothing but a senseless, pointless lust, the kind he’s never been inclined to indulge in, but for a moment he’s tempted to draw out this moment of unprecedented contentment and reach down between his legs--

His pleasant haze is stripped rudely away as Chara leans over him, grinning with wicked delight.  _ You okay?  _

“Ugh,” Cross grunts, swatting a hand through the human’s ghostly form as he rolls away from them, any trace of desire thoroughly and immediately quenched. Irritably, he pulls his shirt back into place, ignoring the way his ribs prickle in discomfort.There’s a film of sweat over his bones that itches unpleasantly, making him feel strangely over-sensitive. “M’fine.”

_ You sure? _ It’s not concern driving Chara’s incessant questions, just a gleeful interest in his discomfort. Their partnership is more stable now that Cross has Nightmare’s authority to keep Chara in check, but they’re not ever going to be more than tolerant of each other.  _ You were groaning in your sleep. _

_ “ _ I’m fine,” he repeats, more clearly and with an edge of warning. His face feels warm. He hopes he’s not blushing. He knows Chara’s not nearly as young or innocent as his ghostly body makes him look, but there’s still plenty of things Cross hasn’t been comfortable doing since they started sharing a body, and touching himself is definitely one of them. Either Chara doesn’t feel the same lingering, unsatisfied flush that Cross is suffering, or he doesn’t recognise it for what it is. Either way, Cross has no intention of explaining it.

Chara gives an indifferent shrug that doesn’t fool Cross for a moment, but even though Cross doesn’t have much basis to back up his threat Chara seems willing to let it go.  _ You overslept too. That’s not like you. _

It isn’t. Cross sits up and feels the room spin slightly with the abrupt motion. He shakes his head, trying to clear it. “Damnit, damnit…”

He sleeps half-dressed, a habit that’s part soldier’s practicality in case he needs to get moving in a hurry, and half-laziness that he would never hear the end of if Killer of Dust caught wind of it after all the grief he’s given them about their own habits. He tugs on his boots and begins the arduous task of aligning the complicated fastenings of his jacket and cape. 

For all of its ridiculous and overcomplicated embellishments, Cross usually appreciates the protective layers of his uniform, but today the padded weight of his jacket feels stifling and restrictive. Tugging on the straps and resettling the flow of his cape does nothing to ease the odd feeling of wrongness, like something isn’t fitting correctly. It doesn’t help that his bones still feel sticky and heated, but there isn’t time for a proper shower. He barely has time to splash water on his face before his door is unceremoniously kicked open.

“Learn to knock, asshole,” he calls out, aggravation but unsurprised. Killer isn’t known for his patience, nor his respect of boundaries. The lock on Cross’s door has been battered so many times it doesn’t work properly any more, not that it ever did much good. With an exasperated sigh he emerges from the bathroom to find Killer waiting at the doorway instead of having barged in like he usually does.

“Huh,” Killer says, regarding Cross with his eerie, pupiless stare. “I was wondering what was keeping you.”

There’s a hint of something smug and knowing in his tone, like he’s in on some sort of joke Cross isn’t aware of. He covers his confusion with an unimpressed glare. 

“What?” he asks, because Killer is still hovering like he’s at the edge of some kind of invisible boundary, not getting any closer but not getting out of the way either. “Aren’t we leaving?”

Killer’s brow-bones hike upwards, skeptical. “You really wanna go out like that?”

Cross glances down at himself superciliously, but despite his knee-jerk of doubt there’s nothing out of place about his uniform. The straps wind over his chest like they should, his undershirt isn’t still hiked up to his ribs, and his cape isn’t tucked into the back of his shorts or something equally embarrassing. There’s nothing out of place to warrant Killer’s incredulity. The fact that he hasn’t showered should be  _ that _ obvious.

“Though I guess you probably don’t wanna have to tell the boss you’re feeling under the weather, right?” Killer asks, his leer so aggressively shameless Cross almost stumbles back a step. For reasons he can’t put his finger on, it strikes a similar chord in him that his dream did; his nerves plucked like the string of an instrument, thrumming furiously with useless and unresolved intensity.

It makes him wonder if Killer knows, somehow, which is a mortifying thought he doesn’t want to entertain. Besides, a stupid dream and a few heated feelings isn’t any reason to blow off a mission.

“I’m fine,” he grits out for the third time that morning. Each reputation feels less convincing than the last. He tries to shake the unseemly tension out of his shoulders, unclenching his fists to flex his phalanges. “Where are we going?”

Killer tilts his head with amusement, like Cross has found some new and unique way to be stupid, but with a surprising lack of objection he reaches into his inventory to pull out a dusty and familiar looking jacket.

“Ta da!” Killer presents it with a morbid flourish, then throws it at Cross’s face. Cross snatches it out of the air, holding the filthy garment at arm’s length.

“The Sans is already dead, huh?” he murmurs. There’s slight variations between each universe, but the hoodie is clearly recognisable even though its color is more of a dull black than the more recognisable blue. 

“Yup. No pesky interference.” Killer’s smirk is irrepressible. “Guess Nightmare’s still going easy on you.”

Cross’s mouth twitches, not quite a frown. He’s not stupid enough to question Nightmare’s judgement, but a small part of him wishes for a real challenge, and not another test of feigned importance with Killer as his babysitter. He sighs, but reluctantly squints at the jacket until its’ frayed edges break down into flickers of code for him to read.

Aside from Nightmare, he’s the only one who can make portals to other worlds, and unlike their Boss, Cross can’t just travel without direction. He needs a solid set of coordinates before he can carve a pathway between universes. Initially, he’d needed Nightmare to guide him to a new AU before he could travel there on his own, but after some experimentation they’ve found that he can glean its location data from any fragment of code -- from a person belonging to that universe, or even just an item.

There’s a lot of extraneous data attached to the jacket. Cross has to comb over it carefully, the chalky remnants of its former owner smearing on his palms, before he finally manages to locate the information on its origin. His brow furrows as he examines it, because despite its familiar shape the jacket feels too small and light in his grip. For an uneasy moment he wonders if it belonged to a child, but a closer inspection reveals it’s just been cropped in a more licentious style. He shoves it into his own inventory with a scowl of distaste.

“Okay,” he says, closing his sockets to better picture the code in his mind. When he calls up Chara’s knife, its handle makes his whole arm buzz like he’s gripping a live wire. Usually handling their determination-fuelled powers isn’t quite so jarring, but he grits his teeth through the discomfort and slashes at the air, tearing open a jagged hole in the fabric of reality. On the other side of the portal, he can see a dark, filthy street, littered with garbage and steaks that might be soot or the charred remains of spilt dust.

“Nice,” Killer approves, walking fearlessly through the gap like he’s never considered how easily a slip of Cross’s wrist or a forgotten number in the code could leave him walking into a deathtrap, or worse, the endless void between the universes. “I bet you’ll enjoy this place. You’re finally in the right mood for some fun.”

Cross arches a brow of his own, but doesn’t bother with a retort. He’s learned to recognise the patterns in the code enough to realise their destination is a variation of the Fell universe. Unlike Killer he’s never revelled in violence for its own sake. He very much doubts this mission will be any kind of fun, especially not when they’re following Nightmare’s orders.

The second half of the universe’s title isn’t one he’s familiar with. He’s never seen a ‘Lust’ universe before, but he doubts it’ll hold anything of interest for him. 


	2. Chapter 2

The moment Cross steps through the portal, scorching air hits his face with the force of a slap and he knows they must be in Hotland. He can smell the acrid fumes of the core mixing with the sulphuric miasma of the lava flows. Almost immediately he feels his bones break out in a fresh, unpleasant layer of sweat, a miserable, humid heat soaking into his clothes.

Killer looks unaffected, downright cheerful as he leads the way through the narrow alley. The buildings around them are dilapidated and empty. He can’t hear anything but the lonely shuffle of their footsteps echoing between the crumbling walls and the roof of the cavern.

“So what are we doing?” he asks, keeping closer to Killer than he might normally prefer. He’s not nervous, exactly, just...uneasy. The air is ripe with the promise of dust, and even though he and Killer are likely the most dangerous creatures in this underground, especially with the resident Sans already dead, there’s no sense in being careless. 

“We’re human hunting!” Killer tells him with a cheer bordering on bloodthirsty delight. He gestures grandly to the forsaken buildings. “This universe is one of the boss’s favourites. A nice, miserable dystopia where everyone hates each other. The human spent a long time sticking to the ruins. Didn’t feel like trying to go further, I guess, but recently they changed their mind.”

“They’re trying to get out?” Cross guesses. He doesn’t know the general shape of the underground as well as Killer, but he thinks they’re near the end of Hotland, verging on the outer perimeter of New Home. If that’s the case, the human’s getting close to their objective. 

“Without hurting anyone,” Killer confirms with a sneering lilt to his grin. “They’re doing the whole schtick, singing songs and flexing their friendship muscles. It’s a real shit show.”

Cross nods in understanding. The human’s actions spread like ripples across a still pond, interrupting the unchanging, static existence of the Underground with a hurricane of change. If they chose kindness, their influence would spread like a virus, trying to push the world towards a better, more hopeful ending, and depriving Nightmare of the core of his power. “Boss wants us to kill them?”

“Even better,” Killer says, beaming. “He wants us to  _ convince _ them that maybe leaving the ruins was a bad idea. If we have to kill them...sure. We can do it as many times as it takes for the lesson to sink in. Once they’re ready to roll back the timeline, we can call it a day.”

“Heh. Easy.” As missions go, this is one Cross thinks he can enjoy. He’s never held much sympathy for humans in general, having found most of them to be cruel and ignorant, malicious and spiteful without cause. The human they’re looking for will probably be wearing Frisk’s face, but that’s not any kind of deterrent. Making them bleed, suffer and die over and over...he might even find it cathartic. 

Killer is almost jittering with suppressed eagerness, making Cross wonder what sort of relationship he had with his own human. 

(The bright flare of Killer’s soul hovering against his sternum makes Cross think of those red-drenched dreams. So much bright, hot crimson oozing between his fingers, clotting in his sleeves, and even as the color cools and darkens in the air it still hurts his eyes to look at. His eyelights feel like they’re splitting, fracturing, falling to pieces like the shattering shards of a soul.)

The alleyway opens up into a wider road, splitting in several haphazard directions. Killer pauses, eyeing the array of choices before turning back to Cross. The expression on his face is one Cross has learned to be wary of. “So...Wanna play a game?”

“No,” Cross replies flatly. His blatant refusal makes Killer laugh.

“Call it a challenge then.” Killer’s smile flashes dangerously, knowingly. “You like those, right?”

Cross tries to keep his face blank, but while his stoicism might have worked on his friends, on his brother, it’s never been particularly effective against other Sanses. They see too much.

It’s aggravating how easily Killer can play him, and how Cross somehow lets it happen every time. With the assured confidence of someone who knows he’s won, Killer says, “Let’s see who can find the human first. Boss says they should be around here somewhere. We can cover more ground if we split up.”

It’s not a wholly terrible proposal. Even if Killer is more familiar with this AU, Cross has a few tricks of his own to exploit. It’s still not an entirely fair match, but Cross wasn’t expecting it to be, and the weighted odds would make it a more interesting contest.

“Fine,” he agrees, offering the other skeleton a rare smirk. “You’ll lose, though.”

Killer laughs, clearly delighted. He’s never been one to take their missions too seriously, always preferring to find his own ways of making the experience more interesting. “We’ll see about that.” 

Killer doesn’t have Nightmare’s ability to literally melt into the shadows, but he vanishes almost as seamlessly, moving fast enough that Cross’s eyes struggle to follow him. Killer’s at his most dangerous when he’s alone and unsupervised, though Nightmare is really the only one who can properly keep him in check. They’re not meant to murder indiscriminently since broken souls can’t fuel Nightmare with their negativity, but if anyone else crosses Killer’s path before the human does, he doubts they’ll be getting away unscathed. 

And that works to his advantage, because Killer has a tendency to get distracted, whereas Cross tends to focus single-mindedly on an objective to the exclusion of all else. He’d once wondered if perhaps Nightmare had paired them together explicitly for that reason, to complement their respective strengths and weaknesses. It may have factored into his decision, but the simpler and therefore more likely explanation is simply that Killer seems to find Cross entertaining and is therefore slightly less likely to leave him for dead in a bad situation (or outright stab him in the back for whatever EXP he’s worth).

Cross takes a breath, ignoring the bitter aftertaste of ash and refuse, focusing inward and letting the code of the universe ripple sightlessly around him. It would be too overwhelming to try and look at every individual fragment, and most of it would have nothing to tell him. He doesn’t need to know the precise color variation of each brick or the cubic span of each building. He tries to feel out places where the code has been altered, the little signals of change and reactivity that occur when the human comes near, and without overthinking his effort he strikes out blindly in the direction that  _ feels _ like it might be right. 

He’s still not very experienced at handling the code, but it’s gratifying when Chara fades in beside him, looking intrigued.

_ You’re getting better at that _ , Chara notes, choosing to match Cross’s step instead of floating at his side like a ghost. _ I didn’t even have to show you. _

_ I don’t need you for everything _ , Cross thinks back snippily. It’s easier and more natural to speak to Chara out loud, though he tries not to do it outside the privacy of his room. He wouldn’t be the only skeleton in Nightmare’s castle guilty of talking to himself on occasion, but he’s called his own sanity into question often enough not to want to give others reasons for doing so.

_ I was paying you a complement _ , Chara protests, feigning wide-eyed innocence. It looks so much like the expressions Frisk used to pull back when they knew they were about to get in trouble that Cross’s soul gives an unpleasant twist.  _ No need to get mad. _

Cross doesn’t deign to reply. He knows there’s a lot about their shared powers that Chara is deliberately withholding from him, trying to maintain every possible advantage over Cross now that stealing his body is more trouble than it’s worth. Every time Cross makes headway on his own, Chara stands to lose, so the attempt at flattery only comes off as painfully insincere. It took longer than it should have, but Cross has finally learned not to trust anything that comes out of Chara’s mouth. Whatever he’s trying to achieve by buttering Cross up, he’s determined not to fall for it. 

Ignoring Chara’s phantom presence, Cross rounds a corner and has to shield his sockets from a sudden glare of light. He knows another monster would only see an empty stretch of dirt next to a rusted capsule-like structure that might once have been part of an elevator shaft, but thanks to Chara he can see the save point in all its shining glory. It sparks like an angry firework, fizzling with lines of whirling code that skitter uncomfortably across his vision.

Cross can’t use the save point for its intended purpose, not even with Chara’s determination, but that’s not what he’s here for. Peering carefully into its sparking core, he reads the latest entry branded into its code.

**Hotland - Red Lights District  
** **Frisk - LV 1**

The human was here only minutes ago. They can’t have gone far. Cross grins smugly, straightening up again to survey the area, searching for traces of a more obvious physical trail he can follow. The street is still empty, but he curiously notes that despite the name of the save point, there’s no lights in the street, red or otherwise. Usually the geography in the Underground is subject to the King’s painfully uninventive naming conventions, so it’s peculiar to find a place that doesn’t seem to live up to its title. 

He wonders if it’s supposed to be a puzzle of some kind. Maybe the true facade of the district only shows up once you find the right mechanism, or open the correct door. It’s been a long time since he’s gotten to indulge in a good problem-solving exercise. Maybe if there’s time, he’ll look around to see if he can figure it out. The ‘Red Lights’ sound like they’d be an interesting sight to see. 

A faint noise draws his attention, a hiss of something scraping against the uneven street, spurring Cross into action. He dashes towards it, ignoring the strange heaviness in his limbs as he struggles against the clinging weight of humidity in the air. The temperature has been creeping up on him, growing more intense even though he could have sworn he was moving away from the Core instead of towards it. His breath is already coming faster to compensate, trying to cycle air through his burning ribcage.

He turns the corner and skids to a slightly inelegant halt, his body responding slower than it should. He’s found the source of the noise; not the human, unfortunately. It’s just a monster, and not one he’s familiar with, but as they turn to face him their expression lights up with recognition.

“Hey there, handsome,” the monster greets, slithering closer. The bottom half of their body is a long, serpentine tail covered in a thick armor of scales while the top half is horse-like and sleekly furred, bulging with rippling muscles. Both halves look equally dangerous, their massive frame towering over Cross at nearly three times his height. “Came back for more, did you?”

Dark, glittering eyes peer out at Cross, only to flicker in surprise as they take him in more closely. “Ah...You’re not Sans.”

They seem more disappointed than angry, which is good for Cross because he’s not interested in a pointless fight. 

“No, I’m not,” Cross agrees swiftly, taking a step back only for them to scoot closer, reclaiming the distance. He narrows his eyes, checking them discreetly so as not to incite them into a fight. 

**Aaron - LV 10  
** **Drawn to your smell. He hopes you’re up for a bit of horseplay. ;)**

Embarrassment makes Cross feel even more heated. Clearly skipping his usual shower was a bad idea, although usually it takes a much more significant lapse in hygiene before his bones start to noticeably smell. It must be the unexpected sweating from all the heat. Trying to maintain composure, he gives Aaron an unfriendly glare to deter his interest. “Go away.”

“Don’t be like that,” Aaron croons. His smiling muzzle is full of unexpectedly sharp teeth for a creature based on a herbivorous species. “You’re looking for someone, aren’t you?”

Is he talking about the human? Cross hesitates, which Aaron seems to take as some kind of affirmation. He rumbles approvingly, gesturing at himself and giving a discomforting wink that sets Cross’s nerves on edge.

“I thought so. I know exactly what you need.”

“Do you,” Cross says, unimpressed. 

Rather than taking offence at his chilling tone, Aaron laughs. “If Sans were here, he’d tell you all about it. We’ve had a good time together, he and I. You really look like him. Are you that brother he’s always talking about?”

Aaron’s friendly, conversational tone conflicts with the predatory way he moves closer, confident and fearless. Cross frowns, curling his fingers to bring forth his blade, but instead of the familiar weight of the hilt falling into his hand his whole arm spasms strangely. It’s been tingling faintly ever since he summoned his knife the first time to make the portal, and trying to call his magic intensifies the sensation into a stabbing rain of pins and needles. He winces, clenching his fist against the ache.

Oblivious to his discomfort, Aaron continues, “Sans always told me to stay away from his bro, but you wouldn’t be here unless you were interested. Hasn’t Sans been taking care of you properly?”

_ I don’t think he knows where the human is _ , Chara remarks impatiently. Silently, Cross agrees. He doesn’t know what Aaron wants, but if he’s hoping Sans’s name will make Cross lower his guard he’ll be disappointed. Cross tries for his knife again, channeling his aggravation and unease to try and stabilise his magic.

“Sans is dust,” he says flatly. If Aaron knew the former Sans, perhaps news of his death will shake him. “Like you’ll be if you don’t back off.”

“Is that so?” Instead of looking upset, Aaron only looks delighted. His mouth stretches in a wide, hungry leer. “Then I guess that means there’s no consequences if I claim you for myself after all.”

_ Chara, give me the knife _ , Cross demands tightly, though he’s not sure his faltering magic is his partner’s doing. It’s  _ his _ half of their soul that’s pulsing unevenly, feeling tight and hot in the cage of his ribs like its overwrought and heat-stressed. It shouldn’t be; it’s not even manifested, and even if it was, ambient heat should affect it any more severely than it does the rest of his body.

Aaron reaches towards him just as Cross finally feels a spark across his palm. Without hesitation he slips beneath Aaron’s arm and slashes viciously upward. He’s not trying to kill, just to maim with a slice across the chest to make Aaron rethink bothering him further, but almost immediately he realises he must have held back too much. The knife in his hand isn’t the sword-like blade he usually summons; it’s tiny, barely three inches long, and the cut it makes barely penetrates the other monster’s heavily muscled abdomen. The slice it leaves is thin and shallow, barely more than a scratch.

It’s hard to tell which of them is more surprised. Both of them stare wordlessly at the pathetic cut, but Aaron recovers more quickly.

“Oh honey,” he laughs, a braying cackle of sound. “You want to play a little rough? That’s okay, if you like it better when someone takes it from you, I’m happy to oblige.”

_ Fuck _ , Cross thinks as Aaron sweeps out a hand. He ducks the blow, expecting a simple punch only to be struck unexpectedly with an enormous fist made from magic that arcs out of the air, a scaled-up mirror of Aaron’s own arm. He goes flying, slamming into the side of the nearest building with a painful sounding crunch that he hopes is the shattering of brickwork and not the fracturing of his ribs. It’s hard to tell. His skull is ringing, distorting the feedback of pain as he staggers upright again.

_ What the hell are you doing? _ Chara rants, his voice a soundless scream in Cross’s ear.  _ If you can’t handle it, let me take over. _

_ No,  _ Cross counters, immediate and instinctive. For all he knows, this is Chara’s doing; messing with their shared body to weaken his magic. The wave of bones Cross sends back at the other monster is just as useless as the knife, slow-moving and fragile. It splinters apart against Aaron’s thick tail, not even leaving a mark. 

“My turn,” Aaron gloats, lifting his arms in a posturing flex that produces a pair of giant fists on either side of Cross. He tries to scramble away but he’s already off-balance, vision skewed by the concussive throbbing in his head. One massive hand manages to snatch his trailing arm, yanking him back into reach so the other can wrap around his waist. They lift him off the ground, suspending him in the air.

“Let go!” he snarls, kicking and clawing frantically to no effect. The summoned arm constructs are so enormous they make Cross’s body seem tiny, like a doll in the hands of a greedy child. The one around his waist tightens like a vise, but instead of trying to crush him into powder he feels the thick trunk of its thumb sliding up beneath his shirt, slipping up into his chest cavity. 

“Let’s see if you have the same weaknesses Sans does,” Aaron says, beaming proudly as Cross yelps in scandalised protest. “How does this feel?”

Pressure shifts dangerously up the length of Cross’s spine, driving the breath out of him. For a horrifying moment he thinks it’s going to push against the column of bone until it snaps. A broken back might not kill him thanks to Chara’s determination, but the agony would be unthinkable. Paralysing horror makes him go still, but instead of the expected pain the hand strokes carefully. Cross chokes, spasming in equal parts alarm and overstimulated discomfort. The ventral axis of his spine is rarely touched, especially the portion that sits behind his ribs. Even the lightest caress feels invasive against the hypersensitive span of his thoracic vertebrae. 

“D-don’t-!” he gasps thinly, trying to dislodge the knot of panic in his throat. Aaron ignores him, smugly repeating the motion, and to Cross’s dumfounded shock his soul surges into being, manifesting into physical form entirely without his consent. Even more bizarrely, it's accompanied by a strange, wet splatter that drips down inside his sternum and into his pelvis. It feels hot and thick, like blood, but he can’t crane his head to see. His body feels rigid, refusing to obey as Aaron creeps closer, eyes locked on the light peeking out through Cross’s ribs.

“That’s right,” Aaron murmurs, his tone almost gentle, affectionate. He blatantly ignores Cross’s frantic wheezing, his magic holding Cross in place as he reaches “I know you want this. I promise I’ll treat you real-”

He cuts off mid-sentence, going perfectly still. There’s a knife against his neck, cold silver instead of Cross’s vibrant crimson. Killer is hanging casually from a fist-full of Aaron’s long mane, balancing effortlessly as he presses his weapon against the seahorse’s bulging jugular.

“Hey pal. Mind un _ hand _ ing my friend there?” Killer’s smile looks as blithe and unbothered as always, but for some reason it makes Aaron quail where Cross’s threats had no effect. Sweat dapples across Aaron’s arms and chest at an alarming rate, darkening the fur in uneven patches.

“Oh, sorry. Was he yours?” Aaron tries with a quivering, ingratiating smile. With exaggeratedly harmless slowness, he starts to lower his arms. Cross feels the grip of the constructs loosening. “I didn’t mean to-”

He doesn’t get a chance to finish. Killer dusts him mid-word without a shred of hesitation or mercy. He drops easily back to the ground as the body crumbles beneath him. Cross’s landing is less graceful, almost sending him sprawling as the constructs dissolve along with their owner. He barely keeps his balance, his knees almost buckling as his soul throbbing for attention. It feels like it’s going to jerk right out of his chest, slamming senselessly against the underside of his sternum. 

“Wow,” Killer says cheerfully, brushing the dust off his sleeves. “You really messed that one up.

Chara hovers irritably at his side, looking far more annoyed than Killer does.  _ You really did. What’s wrong with you? Did you crack your head open or something? That was pathetic. _

It was, and normally Cross would be aghast at his own poor performance, but that seems like a distant, trivial concern next to the heavy pulse of his soul. It feels like it’s trying to tell him something, fluttering strangely as he blinks dazedly at Killer. Its rhythmic beat reminds him of morse code, tapping out a message he can’t decipher that feels unbearably urgent.

“Gotta say, I’ve never seen you get distracted like that,” Killer muses, sauntering closer. His eyes flick briefly down to the pale light of Cross’s soul before lifting back to his face, but there’s no hint of change in his expression. Just that implacable, unreadable smile. “Guess we should-”

The nearer he gets, the more Cross’s soul pounds, a rising, maddening tempo that drives every other thought out of his head. Without thinking, he lashes out, grabbing the front of Killer’s jacket and pulling him close until their bodies are flush together. Gratifyingly, Killer doesn’t struggle, doesn’t resist as Cross holds him in place. He isn’t quite sure what he’s doing, but the giddy thrill in his soul tells him this is right, is necessary. The oppressive shackle of heat seems to lift away, as he breathes shakily against Killer, the spark of friction between their bodies coiling into a wonderful tension as he leans down and--

“No,” Killer says, simply.

The word makes Cross freeze in place, somehow registering past even the mindless urgency of his instincts. He stares into Killer’s empty sockets, confused. “W-what?”

There’s a pointed tap against his ribs as Killer nudges him with the knife, but he’s using the flat edge instead of the sharpened point. It’s not the weapon that gives Cross pause, though, but the absolute conviction in Killer’s voice. “Let go.” 

The words are phrased as an order, and Cross’s training kicks in. He immediately retreats, falling back several paces, completely bewildered at his own actions. He’s lucky to have gotten out of Killer’s personal space unscathed. It’s a merciful miracle that Killer didn’t gut him. He would have deserved it for manhandling him --  _ molesting him _ \-- like that.

Instead of retaliating with murderous fury, Killer only takes a strangely deep breath and tells him, “Go home.”

He’s getting off lightly, incredibly so, but for some reason, Cross hesitates. His soul is twisting unhappily, displeased by Killer’s rejection, his distance. “But-”

“I’ll finish this by myself. You’re not in any shape to be helpful.” Killer’s face is eerily blank, even by its usual standards. The lack of eyelights make him especially hard to read, although his sockets narrow when Cross fails to comply, and finally he snaps, “Go.”

Unthinkingly, Cross summons his knife, ignoring the violent throb of complaint that runs up his arm as he slashes open a new portal. He’s not sure if it’s fear or shame that sends him stumbling through it, back into the cold silence of the castle. Even after the hole closes up, it feels like Hotland’s heat is still clinging to him, a burning haze of confusing heat and disorienting smoke clouding inside his skull. He’s panting, unable to think. His body aches, but not from the fight. He doesn’t know what’s wrong with him.

“Cross.”

Surprised, he whirls around to find Nightmare standing behind him. His bright, cyan eye is hooded as he eyes Cross over, taking in his flushed and sweating bones, the traces of scuffing and dust on his uniform.

The exposed glow of his soul.

Nightmare’s mouth turns down in a twist of disapproval. His voice is soft and dangerous as he says, “Do you have something to tell me?”


	3. Chapter 3

Staring back at Nightmare, Cross’s first desperate, unthinkable impulse is to get close to him. To pin Nightmare’s body against the nearest wall and lean into him the way he’d done with Killer. Thankfully some dim survival instinct persists despite the scorching heat currently burning through him. He stays rooted in place knowing that such a move would be unappreciated at best and downright suicidal at worst.

Nightmare’s impatient sigh reminds him that there’s a question to be answered, but for the life of him Cross can’t remember what it is.

“You’re back early,” Nightmare states flatly, like Cross is a child who needs the obvious explained for him. Nightmare’s head tilts, cyan eye flickering softly, and Cross can practically feel the unseen slither of his boss’s senses reaching out across the multiverse. “And yet my orders haven’t been completed.”

“Killer sent me back,” Cross replies, hoping that’s enough of a justification. If he’s forced to explain why, he’s not sure the answer is anything he can put into words. He can’t think or concentrate with the way his senses are still pinwheeling between utter numbness and painfully acute sensitivity. He can smell Nightmare, even from across the hall. He’s never even noticed Nightmare _had_ a smell, but it’s sweet and smokey with a bizarrely fruity tang, like burned apple pie. It’s making Cross’s mouth tingle with want.

“I see,” Nightmare says. His expressions have always been particularly inscrutable, but Cross can’t even hope to read him now. His intense stare makes Cross shift uncomfortably, feeling awkwardly aware of the sweat trickling thickly down the inside of his ribs like the teasing slide of someone’s fingertips. “I suppose he determined you were no longer capable.”

“I…” The protest comes instinctively, but there’s no conceivable excuse for failure except his own incomprehensible actions. He doesn’t know how to explain himself. He should also be a lot more concerned about the fact that his magic isn’t working properly, but all he can think about is how his chest feels too tight to draw a full breath but every inhale tastes sweetly of Nightmare. It’s too much and not enough. He feels light-headed, high on the tartness of apples. 

“Though he should have known better, too,” Nightmare continues as if Cross hadn’t spoken, not that Cross has anything of value to contribute. His attention is fixed on the cruel twist of Nigthmare’s smile. “I’m surprised he managed to convince you to go out in such a state.”

Cross’s thoughts feel as slow as molasses as he belatedly asks, “My...state?”

“Your heat,” Nightmare says, as if to clarify.

“Heat?” he repeats again, a moronic echo. Cross can only assume Nightmare’s referring to the clinging grip of fever that seems to have taken hold of him. He’s starting to realise it’s not wholly the fault of his visit to Hotland. That warmth would have dissipated by now, but Cross can clearly feel that his own body is still burning without any outside influence. His chest feels especially hot, his ribcage a sweltering furnace around the scalded shape of his soul.

For some reason, Nightmare’s look turns sharp. “That’s right. Don’t tell me you didn’t notice?”

He takes a step closer, and every part of Cross goes tight with tension. He can’t tell if his instinct is for fight or flight; it feels like both, but years of training takes precedence and his posture remains still and unbending as Nightmare comes within reach. A tentacle curls across his forehead like it’s taking his temperature. It feels blissfully cool. Cross’s sockets flutter shut, basking in the brief relief. 

“I don’t...know what you’re talking about,” he murmurs, dazedly leaning into the faint pressure. 

It’s easier to confess his ignorance when he doesn’t have to brace for the disappointment and disgust in Nightmare’s expression. For all of XGaster’s promises of perfection, Cross has seen enough of the multiverse to know that his universe was only ever allowed to develop in a limited, controlled fashion. Anything that didn’t fit XGaster’s ideas was discarded or removed. There’s absurd holes in Cross’s knowledge, things that seem so natural and normal to other universes that are completely outside his experience, even with the memories of multiple timelines to fall back on.

The blessed tentacle is withdrawn, and Cross’s eyes blink open to reveal Nightmare looking strangely perturbed. “You don’t know-?”

Unexpectedly he stops, taking a moment to scrutinise the hallways around them. There are few residents in the castle, but the empty hallways have a tendency to echo and the shadowy corners are an open invitation for habitual eavesdroppers. Cross’s senses are too dull and useless to determine if there’s anyone in the vicinity, but Nightmare looks displeased. He grabs Cross’s wrist and unceremoniously drags him through a portal leading to his office. It’s where Nightmare keeps any reports he’s gathered on the multiverse, and where he conducts anything that can be loosely described as official business. 

It’s also the room where he doles out punishments when his plans go awry. Normally that knowledge would unsettle Cross, but his thoughts seemed trapped in a feedback loop of discovery. He’s touched Nightmare’s tentacles before, but never realised how incredibly silky-soft they are. The supple coil around his wrist is slippery smooth and delightfully pliant. He wants to squeeze it to explore that texture further, but before he can act on the impulse he finds himself abruptly released as Nightmare pushes him down into a chair.

“Cross.” Nightmare stands over him, arms crossed over his chest. “How old are you?”

Cross bristles. “Old enough!”

Even Cross’s inexplicable urge to reach out and touch Nightmare again is quelled by the utterly unimpressed look his boss gives him. He hunches down on himself and grudgingly confesses, “Twenty-nine. Why?”

His age has always been a bit of a sore point. Even to other monsters, his short height and round features tend to make people think he’s younger, especially when he’s with his brother. On the other hand, there’s not much difference between him and the rest of Nightmare’s crew, so it’s even more irritating when the others deliberately coddle him simply because he’s new and his LV is lower than theirs. 

“Then you’re definitely old enough to know that heat is the mating imperative for monsters,” Nightmare tells him. “At your age you should have experienced it several times since reaching adulthood.”

Cross’s befuddled silence is enough to answer the implied question there. He’s never experienced anything like this, and he’s not sure why a ‘mating imperative’ would make him feel like he’s burning up, though it may explain his sudden urge to be more touchy with people he definitely shouldn’t be. He opens his mouth to ask a question, but Nightmare is already continuing. 

“Given the sheer potential for variation between universal constants, I suppose it’s not surprising that it may not exist in some places. I believe it’s also less common for monsters with chronic health conditions. Disease, malnutrition...hmm, possibly soul afflictions? But your condition only occurred recently, so you still should have...”

Nightmare’s thoughtful monologue trails off into more incomprehensible mutterings, or perhaps it's only that Cross’s attention is completely entranced by the way Nightmare leans closer, inspecting Cross like he’s searching for an answer to a puzzle. Cross is agonisingly aware of how little space there is between them, and he desperately fists his hands in the fabric of his shorts instead of into Nightmare’s jacket like he wants to.

Lost in thought, Nightmare doesn’t seem to notice Cross’s aborted motions, but he can’t ignore the high thread of sound that slips unintentionally from the back of Cross’s throat. They both freeze. Seconds pass, and it feels like all of Cross’s heat has migrated up to his cheekbones before Nightmare gives a resigned scoff.

“I suppose it doesn’t matter,” Nightmare says, finally pulling away and moving back to a distance that allows Cross some measure of breathing room. He can’t tell if he’s relieved or disappointed. “You’re clearly experiencing it now, which means that for the time being you’ll be useless to me.”

Cross flinches. “What? Boss, I-”

Mercilessly, Nightmare continues, “Your magic is unstable and you’re not thinking clearly. A monster’s heat also has unfortunate side-effects on others in your proximity so at best you’re a hazard to us all. Return to your room. I’ll have to reschedule the next week around this inconvenience.”

It’s an irrefutable argument, and a clear dismissal. The fact that Cross doesn’t want to leave -- struck by the wild thought that he could corner Nightmare back against the desk -- is only more proof that Nightmare is right and that he should. Cross rises on shaking legs and turns before Nightmare can see the stricken conflict on his face, though doubtless his feelings are utterly transparent to an empath sensitive to every nuance of negativity. The only thing that’ll lessen Nightmare’s awareness of his mood is distance, so Cross leaves to retreat to the safety of his room.

With the door closed behind him, he can finally sink to his knees and just let the violent shudders roll through him. He feels miserable, and not just because of the heat. He hates feeling like a disappointment, like he’s weak. This shouldn’t be happening to him. It’s never happened before!

 _Of course not_ , Chara mocks, easily picking up on his frustrated recriminations. _Do you think_ **_he_ ** _would have wanted to see you like this?_

Cross takes a shaky breath, turning to glare at the smirking phantasm of his unwanted human companion. “You know something about this, don’t you?”

 _Me?_ Chara askes with wide-eyed innocence. At Cross’s low, warning grow, Chara laughs and gives an expansive shrug. _Okay, sure. You got me._

It’s always frustrating to find yet another thing Chara has neglected to tell him, about the multiverse, about their soul and powers, about himself. It would be easy to get side-tracked with his frustration, but Cross is slowly leaning not to lose control of his temper so easily. His new LV makes it difficult, but acting without thinking is one of his most glaring weaknesses. 

“Heats never existed in our universe,” Cross says with conviction. His memories from past timelines are blurred and patchy, but he knows he’s never heard of anything like a _mating imperative_ for his species. The idea is unsettling.

 _Of course not_ , Chara agrees, his face morphing into a sneer. _XGaster wouldn’t want something like that spoiling his precious, perfect universe. He wrote that little trait out of all creations._

“Then...why am I getting it now?” Nightmare had sounded so certain in his assessment, but for a wild moment Cross clings to the hope that maybe the Boss was wrong for once. Maybe it’s only a fever, albeit a very intense one that’s making his bones feel sensitive and yet the only thing he wants is someone to hold him and reassure him that it’ll be okay…

Distracted by the tangent of his thoughts, he almost misses the proud satisfaction in Chara’s eyes.

 _He wrote it out...but Frisk and I wrote it back in!_ Chara laughs brightly at Cross’s appalled expression. _Don’t look so upset. We didn’t know what that code was for. We just knew he didn’t like it and wanted to see what he would do about it if we put it back in. Our last timeline was the first chance we got to do it. I always wondered why he never got rid of it himself, but I guess by then he couldn’t._

Because Gaster had given up his soul, and his ability to Overwrite, or so Chara had told him. The reminder of that conversation makes Cross’s head ache like a distant migraine, or maybe it’s just because of how tense and brittle he feels. Absently, he wipes at the sweat dripping into his sockets with his sleeve. The damp fabric clings uncomfortably to his wrist, reminding him of how unpleasantly heavy his uniform feels. 

Chara considers him thoughtfully. _You would have had about six heats by now, but every time it came up, in you or in anyone near him, he made us alter the code to push it back. He didn’t want us deleting anything. I guess he didn’t trust us not to destroy his work. All we did was change the timing a bit, so..._

“So what?” Cross asks, finally dragging himself back to his feet. It’s immensely difficult to follow the conversation when he feels like he’s burning up. He fights for a moment between the hope that this is something he can overcome with sheer willpower and the growing realisation that he really can’t. He curses the complicated ties of his uniform, almost ripping the seams in his urgency to tear off the outer layers. He kicks them to the corner of his room in disgust, feeling unaccountably frustrated. 

Chara’s grin widens wickedly as he follows Cross, floating uncomfortably close. _So I guess that means you’ve got six heats saved up to get through all at once. I bet that’ll be fun._

Even though Chara doesn’t have a body to generate heat, his nearness feels uncomfortably sifling, and unlike with Nightmare or Killer, Cross doesn’t feel any desire to touch him. With a low growl, he bats a hand through Chara's ghostly form, trying to dispel his image. Chara dodges away from him with a mocking cackle.

 _What’s the matter?_ Chara teases. _Feeling...hot tempered?_

Normally a pun like that would make Cross smirk, but all he can think is that hanging around the rest of the Sanses has been a bad influence on his human partner. He tugs indecisively at the collar of his undershirt before giving in to the inevitable and yanking it off. He feels marginally better without it, but the air of his room feels still and stagnant. He’s never known the temperature of the castle to fluctuate, staying near-constant in its isolating chill, but right now his room feels like it’s sitting in the middle of the Core. A breeze would be wonderful, but his room lacks either windows or a fan to offer any sense of relief.

“Get lost already,” he orders Chara, kicking off his shoes for good measure. Everything feels too heavy, suffocating and prickly against his bones. He’s tempted to get rid of his shorts as well, but even in the sanctuary of his own room he doesn’t feel comfortable being completely naked and vulnerable. Killer’s already demonstrated his complete disregard for the sanctity of barred doors, and even if he could trust his lock to hold that wouldn’t keep out Nightmare, who might yet have more to say on either the matter of Cross’s condition or his poor performance on the mission.

For a moment, Cross’s thoughts stall over that realisation. If Nightmare were here, if he found Cross alone and naked and wanting, what would he do? Maybe he’d find Cross’s bare, sweat-dappled bones interesting. Maybe he’d want to touch…?

“Hngh...” The image is vivid enough to make his pelvis throb. He can feel something wet trickle down his femur and he hopes fervently that it’s just sweat. 

_Ew_ , Chara says, haplessly subjected to the unfiltered impulses of Cross’s imagination. _I mean, he’s covered in slime and has all those tentacles. Do you really want him touching you with those?_

“Stop talking,” Cross replies with more than a little desperation. He’s trying _not_ to think of it, with very little success. He’s been manhandled by Nightmare’s tentacles in the past, usually when the boss is in a poor mood. Nightmare’s tentacles are unfathomably strong, but also soft and supple and flexible and precise and--

His knees shake, warningly. He braces himself against the bed, trying not to crumble to the floor. “And go away. I mean it.”

 _Fine. But only because you’re being disgusting_ . Chara fades sulkily from view. _Take a cold shower or something, and don’t do anything gross with our body._

Disgruntled, Cross decides he might as well try showering, if only for the opportunity to cool down. 

Unfortunately, he finds his body doesn’t like this idea at all. His first few seconds under the spray feel like he’s being pelted with needles. He yelps and jerks back, fumbling with the taps until the icy flow is replaced with something more temperate. It’s a slight improvement, but the pressure of the water is still too much for his over-sensitive bones even on its lightest and gentlest setting. He cringes beneath it, forcing himself to endure the merciless deluge as he half-heartedly scrubs at his bones.

In spite of Chara’s derisive objection, he tentatively reaches down the expanse of his ribcage, his hands clumsily tracing the rim of his pelvis. Nightmare’s explanation of heats had been sparse, but Cross’s instincts were frantically trying to fill in the gaps. He doesn’t have a chosen partner, and he definitely doesn’t want to conceive a child under his current circumstances, but even if mating isn’t the goal maybe his body will be satisfied if he can feign the act alone…?

His phalanges brush tentatively against his pubic symphysis, but for all its sensitivity the only thing he can feel from his own touch is a flare of rasping pain, like his body knows he’s trying to cheat it out of his true objective. With a hiss of displeasure, he withdraws, hunching under the shower’s unenthusiastic dribble. He barely lasts long enough to rinse off the worst of his sweat before he’s forced to give up, huffily shutting off the water like it’s at fault for his current discomfort.

He doesn’t bother to towel off, hoping the evaporation might help to cool him where the shower itself has failed. He reluctantly pulls his shorts back on, wincing from even the barest pinch of the elastic at his tender hip bones. Everything aches, but it’s especially bad at the base of his spine and around his pubis. It feels like the entirety of his magic is being drawn down to his pelvis, answering the flicker of tenuous arousal he’s trying to ignore. He stubbornly redirects it, trying to pull his magic back into his soul. It makes the weight in his chest feel worse, but he grudgingly assumes that’s just a feeling he’s going to have to get used to.

Stumbling back out into his bedroom, he feels at a loss. He’s both completely exhausted despite having barely exerted himself at all, whilst also feeling full of a restless, directionless energy. Normally he’d be tempted to go down to the training rooms to practice with his knives until he’s properly worn out, but with his magic responding poorly he doubts his efforts would be very effective. 

There’s an itch of need in his bones, and even though he can make a fair guess at what he’s really craving, surely he can find a less mortifying substitute. Maybe food will help calm him down, because right now he feels like he’s in a state of withdrawal for something he doesn’t want to put a name to.

What he really craves is something cold. Did they still have leftover nice cream in the fridge? Nightmare is strangely fond of it. He likes to sneer at the positivity scrawled into the wrappers. All Cross cares about is that it will be cold and refreshing on his tongue, something thick and creamy to suck on that he could make last as long as he’s careful with his teeth…

“I hate this,” he grumbles to himself, heading for the door. He’s so distracted with his goal, it takes a few moments to realise that instead of turning smoothly, the handle only clunks unhappily and stays locked in place. It won’t turn. He flicks the abused lock back and forth, confused, but the door still won’t open for him. He’s trying to imagine how it could have jammed so thoroughly that even shoving his shoulder against it only makes the frame rattle when a bored sounding voice calls from the other side, “Knock it off.”

“Dust?” he asks, bewildered. “What’s wrong with the door?”

“It’s locked, obviously,” Dust replies, careless and indifferent. “Boss’s orders. Told me to keep an eye on you to make sure you stayed put, so don’t do anything stupid. I wouldn’t want to have to hurt you.”

Cross takes a half-step back, less affronted by the hint of anticipation in Dust’s threat than he is at the accusation that he would deliberately ignore one of Nightmare’s orders. 

“But...why?” If Nightmare wanted him to stay, he could have simply said so instead of blocking the door and posting a guard. 

Dust lets out an effusive sigh. “Because heats are contagious, dumbass, and you’re already not thinking straight or you wouldn’t be going out half-dressed. You walk out here with all those bones on display and Horror’ll take it as an invitation. I’m pretty sure him gnawing on you’s not the kind of attention you want. Unless you’re kinkier than I gave you credit for.”

Cross splutters, folding his arms across his naked rib cage. Killer had warned him early on that keeping covered up was the best way to prevent Horror from getting ideas. Exposed skin and bone often made him forget that food was plentiful enough that he didn’t have to worry about taking advantage of an easy meal. “H-how would you know if I’m dressed or not?”

Dust’s chuckle was low and dry. “Wouldn’t you like to know? No, I bet you would. Maybe you like the idea of everyone getting a good look at you, all bare and on display.”

Cross stumbles back half a step, not sure if he's outraged at the implication or just as desperate for the attention as Dust is implying. His knees feel weak. He wonders if Dust can see him now, flushing and uncertain, clearly unable to put up much of a fight if the other monster decides to simply take what was on offer-

A scoff from the other side of the door puts a halt to his reckless train of thought. “Yeah, you’re definitely out of it. There’s no soundproofing in this shithole. I heard you get out of the shower and took a guess since all those layers you like would be miserable in a heat. Don’t get excited. You’re on lockdown until your heat’s over. Boss doesn’t want you taking anyone else off-duty.”

“Oh,” Cross says, hating the faint disappointment in his voice. It isn't like he _wants_ Dust to look at him, or touch him, but--

(Anyone will do. He needs it, he's burning, his marrow is boiling, it's unbearable, maybe if he begged Dust would change his mind? Maybe-?)

“You should sleep it off,” Dust says, an offhand suggestion without any trace of sympathy as far as Cross can tell. More brightly he adds, “Or jerk off. You’re in for a nasty couple of days.”

“Asshole,” Cross grits out, turning around. He isn't obeying because he wants to, or because Dust is telling him to, and he sure as hell isn't going to jerk off knowing how easily he can be heard through the door. It just feels like sleep is the only recourse left for him, the only thing that might help him endure the rest of this humiliating experience before he gets carried away wondering if Horror chewing on his bones would be so terrible after all. 


	4. Chapter 4

The fabric of Cross’s pillow feels coarse and sticky, clinging to his mouth and nose like a stifling hand as he pants raggedly against it. His hands fist in the sheets, grappling desperately for any kind of anchor as he rocks his hips back, tailbone angled upwards and femurs spread wide as he searches for any sort of friction to grind against.

_ Okay, this is just getting embarrassing _ , a sour voice mutters. Cross feels a ghostly squeeze on his soul, the signal of Chara trying to get his attention.  _ Hey, idiot. Wake up already. _

“Hmm?” Cross mutters blearily, slowly rising out of the muggy grip of sleep. The weight he’d imagined pinning him down onto the mattress vanishes, proving to be the figment of a dream. Only the heat still lingers, and he hisses at the aching tenderness of his bones as he groggily tries to orient himself. “What…?”

Chara is floating beside the bed, arms and legs both crossed as he stares at the floor. It’s difficult to tell when Chara’s body is mostly transparent, but Cross thinks the hue of his cheeks might be a little darker than usual.  _ S’not like you were getting proper sleep anyway. You’ve been rolling around and groaning for an hour. It was getting annoying _ .

Cross blinks uncomprehendingly at Chara before looking down at himself. All his bedding is soaked, tinted faintly with the purple sheet of his sweat. His blanket has been twisted into a tight rope that’s thoroughly entangled around his spine, pelvis and legs. His shorts have stayed on but only barely, almost slipping down his hips to reveal far more bone than he’s comfortable with Chara seeing. With a faint blush of his own he swiftly tugs them back up to their proper position and rasps out, “No one asked you to stick around.”

_ I was bored _ , Chara grumbles, turning away while Cross tries to untangle himself from the sheet.  _ It’s not like I  _ **_want_ ** _ to see you like that. If this is what monster heats are like, no wonder  _ **_he_ ** _ didn’t want them in our world _ .

“Then you shouldn’t have put it back,” Cross snaps as he finally frees the last coil of the blanket from his femur and kicks it onto the floor. After a moment of consideration, he gets up and strips off the rest of the sheets as well, since they’re all wretchedly damp and smell pungently of bones and magic. It’s so potent, he actually feels light-headed from the way his own magical musk is saturating the air.

_ You’re a lot moodier than usual _ , Chara notes, turning back to watch Cross with an uncomfortably sharp gaze. A small smirk plays about his mouth.  _ Would it cheer you up to know Nightmare checked in on you? _

Cross wheels around. “What!? When!?”

Chara’s smirk is infuriating.  _ Oh. A while ago. He left some stuff for you. _

He points to the low stand beside the bed, and Cross’s breath catches, thinking how close Nightmare must have been without him realising. Of course the locked door wouldn’t have barred him entry; he can melt in and out of the shadows anywhere in the castle with only the softest slither of sound. For a moment, Cross’s body goes rigid with the thought of Nightmare leaning over him, watching dispassionately as Cross was writhing against his tangled, sweaty sheets. He swallows back the sudden knot in his throat, feeling both flustered and wistful and not wholly certain either is the right reaction he should be having.

Shaking off the intrusive thought, he focuses on the table itself which was bare when he fell asleep, but is now piled high with an assortment of new items. There’s tall bottles of water, a neat stack of foil wrapped ration bars, and strangely, a small plastic bottle filled with a single green pill. Beside it is a sheaf of paper bearing Nightmare’s distinctly cursive and elegant handwriting. 

_ Take the pill and eat. _

Curiously he unscrews the bottle cap and lets the poll roll out onto his palm. It’s about the size of a gumball, moss-green and thrumming faintly with some intent he can’t discern. 

Chara hovers over his shoulder, looking dubious.  _ You’re not really just gonna take it, right? You don’t even know what it is. _

Spitefully, Cross shoves the pill in his mouth. It dissolves instantly, seeping into his magic, leaving behind a faintly bitter aftertaste. He waits a few seconds -- usually monster medicines act swiftly and noticeably -- but he doesn’t feel any different. He’s actually disappointed. He’d hoped maybe it was something that would help with the unpleasant burn of heat in his marrow.

_ Huh _ . Chara shares his bemusement.  _ I kind of figured it would do something awful, given how much he enjoys our suffering. _

“The Boss wouldn’t do that,” Cross objects, defensive. Sure, Nightmare isn’t necessarily kind, but he’s at least practical in the handling of his subordinates. He may have specifically chosen them for the ease with which he could feed off their negative feelings, but he also helped keep those same feelings in check so they could function as best their warped souls and high LV allowed. It was a mutually beneficial partnership.

The supplies he’d left likely served the same purpose -- another aid to help Cross recover so he could continue to serve. Even so, Cross feels faintly touched by the unexpected gesture of what could loosely be construed as concern. 

_ You really think too highly of him _ , Chara mutters, picking up on the thought.  _ Just eat already, I’m hungry. _

Chara doesn’t really need either food or sleep, but he’s always quick to complain about it when Cross is short on either. Strangely, though, Cross doesn’t feel any hunger himself. The ration bars are a soldier’s staple, used to provide a solid hit of energy and healing in a few bland, inoffensive mouthfuls, but even looking at them just makes his non-existent gut give an unenthusiastic roll that borders on nausea. 

_ Oh come on. Now you’re gonna ignore the boss’s orders? _ Chara jeers.

With a deeply reluctant sigh, Cross picks disinterestedly through the pile only for his fingers to catch on a shinier, more colorful frill of foil. Hidden amongst the plain rations is a bar of chocolate, similar enough in size and shape that it could possibly have been put in by accident if Nightmare were prone to making such missteps. 

_ Oh shut up _ , Chara tells him, cringing from Cross’s flush of smug appreciation.  _ He’s still a jerk. _

With relish, Cross tears the wrapper open and takes a bite of his favourite treat-

-and recoils. He gags, almost dropping the confection as his magic roils violently. 

_ What are you doing? _ Chara asks, disgruntled.

“It’s disgusting.” Cross wipes his mouth and glares accusingly at the chocolate bar, wondering if it was some kind of prank treat. Not from Nightmare, that wasn’t the boss’s style and Horror would never taint food on purpose, but maybe Killer or Dust had slipped it into the pantry for a perverse joke.

But Chara’s expression is incredulous.  _ What are you talking about, it tastes fine.  _

Cross stares back at him, perturbed. They share a body. Usually their perceptions are identical, although Chara doesn’t have a lifetime of monster experience to interpret all the magical nuances Cross feels, and likewise Cross’s perception of the code through Chara’s awareness is guided more by clumsy instinct than understanding. Simple sensory input, though, like taste and touch has always been straightforwardly similar. 

Dubiously, Cross gives the chocolate bar a tentative sniff and then carefully touches it back to his tongue. Chara’s right; it’s not the taste that’s wrong. It’s just that Cross’s magic won’t accept it, buzzing angrily at the contact, refusing to accept and absorb the foreign matter like it normally would. He can only imagine it’s another bizarre symptom of his heat, though at least the rest of his body is in agreement that he’s not hungry enough to try and force the issue. He puts the chocolate bar aside, much to Chara’s outrage. 

_ This is the worst. Your stupid body! Why is this happening! _ Chara rants, kicking furiously at the furniture even though his ghostly body just passes through it without effect. Despite the tantrum and flailing, however, Chara looks the same as ever. He doesn’t look to be suffering from the same unpleasant, sweltering heat as Cross.

_ Of course I’m fine _ , Chara scoffs.  _ Humans don’t have heats. You’re not gonna see me humping the furniture like you. _

Spluttering, Cross turns away even though doubtless Chara can feel the burn of embarrassment on his cheeks and the shameful clench of his soul. The faint pressure sparks a thought, and curiously he pulls his soul out to inspect it. Its mismatched lobes beat in an asynchronous rhythm, Chara’s bold, violent red pulsing aggressively against his pale half. Chara’s soul fragment looks just as it usually does, but his own is glowing and flickering urgently with an urgent light, like it’s trying to broadcast a signal. His soul fragment is dripping faintly with excess magic, a thicker and more viscous substance than the sweat on his bones. It’s an unexpectedly confronting and obscene display, and he quickly shoves the construct back in his chest so he doesn’t have to look at it.

It’s not fast enough. His body shudders with a sudden heated flush, like he’s standing too close to one of Hotland’s lava pits. The surface of his bones feel pinched and sore, like all the moisture is being drawn out of him, leaving him a scorched and fragile husk. It’s so damn hot in his room, claustrophobic and sweltering. He’s desperate for just a breath of fresh air, any shift of a cool breeze to relieve him. Dizzily, he stumbles over to the door and knocks urgently. “Dust?”

There’s a faint rustle from the other side, then a droll, flat reply. “Nope. Try again.”

It’s Horror’s voice. They must be keeping guard in shifts, as if they really expect Cross to give them trouble. It’s not that Cross intends to disobey orders, but he’s burning up. All he needs is a few minutes outside, just to get away from the pervasive heat and musky smell of his overwrought body in the enclosed confines of his room.

“Horror. Open the door.” Cross tries to sound assertive, but his voice gives an unwanted waver.

The answer is immediate. “Nope.”

Cross leans against the door, as if being that fraction closer to freedom will help. “I just need some fresh air. Just a few minutes, come on!”

“Nope.”

If he listens carefully, he can hear the soft whisper of Horor sharpening his axe in gentle, rhythmic strokes, unperturbed by Cross’s pleading. The sound of hissing friction makes a shiver run up Cross’s spine. 

“Horror...” This time it’s indisputably a whine. It makes him feel like a child again, arguing futility against Gaster’s unassailable facade. Thoughtlessly, his phalanges curl against the surface of the door, scratching mindlessly at the wood. “ _ Please _ !”

It’s somehow worse now that he’s close enough to catch the tantalising scent of the outside --  _ of Horror _ \-- through the crack beneath the door. It’s a strange, cold smell like the inside of a meat locker, a sharp, sour tang of metal and blood with the astringence of over salted jerky. It’s not a combination Cross would normally find appealing at all, but it promises a soothing counterpoint to the suffocating humidity of his room.

It feels like his thoughts are boiling around on the inside of his skull, senseless with desperation. Wildly, he offers, “I’ll let you bite me.”

There’s a poignant stutter as the whetstone’s movement hisses to a stop. “...What?”

_ What?! _ Chara echos, utterly appalled. Cross doesn’t care, ignoring the prickling itch of Chara’s ghostly fingers trying to strangle him to silence.

“You can bite me,” Cross promises recklessly. “I can just heal it with code anyway, right? It’s not a big deal. All you have to do is let me out.

There’s a profound silence from the other side of the door. 

Chara isn’t nearly so reticent.  _ Cross, what the hell! Why would you say that? What kind of idiot are you? This heat is really boiling your stupid brain- _

There’s a faint shift from outside, like Horror is getting to his feet. Cross presses himself hard to the door, tight with hope.

“When Dust said you were out of it, I didn’t realise it was this bad,” Horror says, slow and thoughtful. “That’s really not an offer you want me to take you up on. S’not happening, kiddo.”

Cross gives a frustrated whine, rattling the handle like maybe this time it’ll give on its own. He doesn’t understand why Horror would refuse. It seems like a perfectly reasonable deal to him. Horror’s bitten him once before, by accident, and it wasn’t  _ that _ bad. Sure, his blunt teeth hadn’t made a very clean incision into his marrow, but within the hour Cross’s code had restructured itself to delete the injury without a trace.

“I’m not opening the door,” Horror repeats more sternly when Cross continues to yank pointlessly on the handle. “Go take a cold shower. Try jerking off. You’ll thank me later.”

_ Come on, you big idiot.  _ Chara’s fingers dig into his arm, and though the human can’t really grab Cross, with enough willpower he can make his touch seem to squeeze unpleasantly.  _ You’re dripping all over the floor. _

Cross looks down and discovers that he is. There’s a growing pool beneath him, of...sweat. He hopes it’s just sweat. There’s a wet film over his body that feels disgusting, soaking into his shorts.

_ Shower _ , Chara demands, and the reinforcement of Horror’s order finally convinces Cross to pull away from the door and stumbles reluctantly towards the bathroom. For a moment, he blinks dazedly at the fixtures, trying to remember what he needs to do. It takes a great deal of huffing and gesturing on Chara’s part to guide him towards the shower and turn the correct tap. It takes a few seconds of standing under the water before he belatedly realises his shorts are still on. He absently shucks them down, kicking them to the corner of the stall.

Chara makes an undignified squeak of sound.  _ Right, you can handle it from here. Don’t drown yourself or whatever! _

He vanishes more abruptly than usual, but Cross barely takes note of it. Even though the drizzle of the shower feels like a rain of needles against his bones, the cold bite of it is an undeniable relief. He lets out a shaky breath, glancing down at where the water swirls the drain, tinted faintly with the color of his magic. All his joints are faintly hazed with its glow, and there’s a swirling cloud of it sitting in the cradle of his pelvis, dark purple with strains of red like a vivid bruise. With a shaking hand, he reaches down, thinking to try and dispel it but the moment his fingers brush the edges of the cloud he feels a potent tingle that makes his knees shake. He barely catches himself on the wall, his breath squeezed out of him in a shaky moan.

_ Jerk off _ . Both Dust and Horror said he should, like it would help him, so hesitantly Cross curls his fingers through the mist again. It’s deliciously sensitive, throbbing warming around his fingers like it’s on the verge of coalescing into something more tangible. Satisfaction feels painfully close, but the moment he tries cupping his hand around his pubic bone the throb becomes unpleasantly sharp. He hisses, trying again with more gentleness, but not only is the contact hot and uncomfortable, but the scrape of his phalanges feels like he’s scouring himself with sandpaper. Discouraged, he tries swirling his magic again, but as eagerly as the haze is suckling on his fingertips it’s not enough. The pleasing tingles only turn into a sharp ache that he can’t seem to relieve, because every time he tries to touch himself more directly it only hurts.

His frustrated attempts are interrupted by a faint sound -- a rattling click that sounds like a closing door. Startled, he turns off the water, belatedly hoping the sound of the shower was loud enough to cover the sounds he was making. He faintly recalls what Dust said about the lack of soundproofing, and balks at the thought that maybe Horror was drawn to the sounds of his pathetic growls and whines as he’d fumbled with his uncooperative bones. 

(Did Horror have second thoughts about Cross’s offer? Had he felt compelled to check on Cross, to see if he was following that off-hand suggestion -- one that could have easily been construed as an order? He could have peeked in from the doorway, his presence and scent disguised by the shower’s steam, watching as Cross as he tried to coax pleasure from his magic-)

With haste, Cross scrambles out of the shower, barely pausing to snatch a towel to cover himself and keep the splatter of dripping water to a minimum. His bare feet nearly slip on the tiles, but when he bursts back into the bedroom it’s disappointingly empty. 

But something is different. There’s a new scent in the air, heady and intoxicating, overpowering his own lingering musk. Cross follows his nose towards the guarded door, which is still closed, but beside it is a bowl of what looks like some kind of stew, gently steaming and filling the air with its rich scent. He breathes it in, and has to compulsively swallow back a salivating mouthful. 

“Horror?” he calls out.

There’s an answering thump against the door. “Heh. Brought you a little something. I know the boss left you some food, but I figured you might be in the mood for something a little more interesting.”

Cross sits down next to the door and reverently breathes in its wafting scent. Even though his bones still feel too warm, the prospect of this hot dish doesn’t seem to aggravate his heated feeling, and unlike the ration bars the thought of eating it doesn’t turn his stomach. His mouth is watering, and suddenly he’s desperately ravenous. 

“T-thanks,” he manages, hands almost shaking as he lifts the accompanying spoon and brings it to his mouth. The flavour of it explodes on his tongue, sumptuous and savoury, with a faintly bitter note that only whets his appetite more. He thinks it’s the best thing he’s ever tasted.

It’s not that Horror is usually a bad cook . Quite the contrary, he knows more about it than anyone else in the castle, but either he overwhelms his dishes with too many bizarre combinations, combining ingredients with no consideration for the taste or texture, or he tries to use as little as possible, making watery broths that are heavily spiced to cover for their lack of substance. There doesn’t seem to be much middle ground between the contrasting approaches.

The stew in the bowl looks like it should fall into the latter category, but there’s nothing lacking about it. There’s only a few chunks of crudely sliced vegetables in a deep, dark gravy that feels gratifyingly heavy on his tongue. Itls packed full of Horror’s intent, hard enough to concuss, and even the flavour is slightly reminiscent of him -- those savoury notes enhanced with the spice of cloves and pepper, sumptuous and delicious. 

“Heh. You like that, huh?”

“It’s amazing,” Cross says between messy mouthfuls, desperate to get it in him as fast as possible. It feels like he’s been starved for days even though earlier he could barely stand the thought of food. Horror’s stew is so incredible he feels almost euphoric, bones rattling faintly as he groans in utter satisfaction. 

“Wow. You decided to give him a good time after all, Horror?”

Cross goes still, the spoon resting awkwardly between his teeth at the sound of Killer’s playful taunt through the door.

Horror huffs in amusement. “Heh. You’re early for a change. Just couldn’t stay away, huh?”

“Gotta get my kicks somehow,” Killer agrees easily. “Anyway, Boss said he had a job for you, so I’ll take over here.”

With a long-suffering sigh and a grunt, Cross hears Horror climbing to his feet. There’s the faint thump of his heavy axe being slung over his shoulder. “He’s been picking up some sweet talking tips from you. Try not to do anything stupid for a change.”

“Who, me?”

There’s a scoff, and the sound of retreating footsteps. He’s so distracted that he actually jumps at the soft, disappointed squeak of his spoon as it scrapes against the empty bottom of his bowl. Cross hadn’t even noticed it was empty already. He sets it aside, and presses himself back against the door. “Killer?”

“Heya, Criss-Cross.”

The door shifts against him like Killer is leaning back against the other side, leaving only a scant two inches of heavy wood between them. For a moment, Cross is rocked by the acute and visceral memory of Killer’s body against his, that exhilarating moment of potential blooming between them before he violently shakes the image away. That moment...was a mistake. He hadn’t known -- still didn’t know -- what might have happened if Killer hadn’t pushed him away and he suspects he should be glad not to have found out.

Cross awkwardly clears his dry throat. “About earlier…”

“Yeah,” Killer injects, like he knows exactly what’s on Cross’s mind. He often does, even without needing to watch Cross’s expression for clues. It’s usually immensely frustrating, but now he’s weakly grateful to be spared some of the embarrassment of having to explain. “You kinda took me by surprise there, but I guess you weren’t expecting it either. Boss says you’ve never had a heat before?”

“No,” Cross agrees, drawing his knees up beneath his chin. He feels calmer now -- more stable. Maybe he had been hungry after all and just hadn’t realised, or perhaps Horror’s intent had helped mollify his agitated instincts. He feels less desperate; less alone. Hesitantly, he offers, “Chara says they were deleted from my universe.”

“Heh. Wouldn’t that be nice,” Killer chuckled humorlessly. “Heats are a bitch, especially when they creep up on you. Can’t really blame you for not having your head on straight.”

Cross had never thought Killer’s voice was pleasant to listen to -- in fact he usually vehemently felt the opposite, especially when Killer was mocking him -- but right now his droll calm is unaccountably soothing. An unacknowledged tension in him unwinds, and he belatedly realises how much it bothered him that Killer might have been angry or offended when Cross had inadvertently accosted him.

(Or maybe he enjoyed it just as much as Cross did. Maybe he still can’t shake off that delightful flush of heat and friction, the weight of promise and tantalizing danger as they sized each other up, going tense with the prospect of a struggle for dominance-)

Cross cuts off the lustful thoughts with a violent shake of his heat, swallowing painfully as he tries to stay focused on the conversation. “Y-you’ve had heats before?”

“Sure. Heaps of times. Had one right before you joined up, actually.”

Perhaps this is the wrong kind of conversation to be having, because that casual admission only makes Cross think of Killer in his position: shaking and sweaty and curled around himself as he’s wracked with trembles of need but unable to relieve it.

“Is it always like this?” Cross asks plaintively. The towel around his hips already feels too heavy and rough. His pelvis burns unpleasantly, and he has to resist the distracting urge to touch it knowing that it won’t actually help. “So...painful?”

“It’s better with someone to help you through it,” Killer tells him. “It settles the instincts. Can even be kind of nice, with the right person.”

That sounds like the voice of experience rather than idle speculation. Cross feels his bones go tight with surprise.

“You had a partner?” he asks uncertainly. He doesn’t know much about Killer, but there’s so many variations of ‘Sans’ throughout the multiverse; surely not all of them have chosen a life of solitude or celibacy.

But the thought of Killer specifically with a mate perturbs Cross in a way he doesn’t want to think too hard about.

“Just a heat partner,” Killer replies, nonchalant. “A fuckbuddy. There’s pills you can take to make sure kids don’t happen, so you can fuck without worrying about it.”

The crass confession makes Cross flush even as he’s reminded of the pill Nightmare left for him. Was that what it was for? But he doesn’t have a heat partner and he doubts Nightmare intends to let him find one, so it must just have been a precaution.

Blithely, Killer goes on, “But there’s always a chance of accidental bonding, even with the meds, so Boss doesn’t like us to risk it. Can you imagine this place turning into a daycare? I mean, he’s a sadist, but crying kids are on a whole ‘nother level.”

Despite himself, Cross snorts a little, faintly amused at the thought of Nightmare with a babybones clinging to his tentacles. He can practically feel the force of Killer’s pleased grin through the door.

“Yeah, didn’t think so. It doesn’t come up as often for monsters with LV anyway, but it’s...more intense, I think. Probably worse for you, since you’ve never had one before, but that’s your shitty luck I guess.”

“Thanks,” Cross grumbles, but in spite of the taunt, it’s actually reassuring that Killer’s treating it so blithely. Perhaps it’s not as big a deal as Cross’s body seems determined to make it out to be -- Chara’s sly expectation that he might be facing the pent up force of six delayed heats notwithstanding. Chara isn’t any sort of expert on heats, after all. He could be wrong.

And Cross is a royal guard. He knows how to endure. If this is something every monster goes through, then surely he’ll be fine.

“It’s just for a couple of days, anyway,” Killer says as if in agreement with Cross’s private thoughts. “It’ll be done before you know it.”

**Notes for the Chapter:**

> A traditional home-remedy for monsters going through a bad heat is to season their food with sexually charged magic (specifically: come) to ease some of the symptoms from the magic and intimacy withdrawal that comes from not having a heat partner.
> 
> Take a guess at what Horror used for making the stew.


	5. Chapter 5

_ You could just let me take over _ , Chara offers, not for the first time. He’s hovering above Cross’s prone form, smirking down at him with more sadistic amusement than sympathy.  _ I bet it wouldn’t suck as much with me in charge _ .

Cross makes a disgruntled noise of refusal, curling into a tighter ball of misery. After stripping his bed, it had seemed like too much effort to find replacement bedding so he’d simply arranged a haphazard pile out of his filthy sheets to lie in. Chara called him a weirdo, but Cross feels strangely more settled close to the floor and boxed in by the wall than he does on the bed.

At this point, he’s grasping desperately at any sense of comfort no matter how bizarre. The brutal heat has returned even worse than before. His magic feels like molten lava in his mana lines, crawling through his bones with a sluggish, vicious burn that’s almost unbearable. Killer’s presence had provided him with a couple of hours of distraction, but eventually he’d swapped out with Dust who has never been much for conversation. Cross’s awkward attempts to engage him were pointedly ignored, and Dust’s refusal to answer was just as maddening as the faint scent of him wafting through the crack beneath the door

Cross knows what monster dust smells like, and Dust does indeed faintly carry the scent of his namesake, but it’s sweeter somehow. Like powdered sugar and fresh snow, mixed with the chalky undertone of death. Finding that appealing is even more discomforting than his new appreciation for Horror’s bloody scent, and the moment Cross caught himself fantasising about burying his face in Dust’s unwashed hoodie he’d hastily pried himself away from the door to put some distance between them.

He’d grudgingly forced down half a ration bar, which didn’t offer him anything like the relief of Horror’s stew, and guzzled from one of the bottles of water while letting a great deal of it splatter down over his sternum and between his ribs. It barely cooled him, leaving him panting and wishing he could simply sleep through the misery like he would with any other fever. Instead, he can only roll around restlessly, vainly trying to find a position that doesn’t put too much pressure on the aching planes of his pelvis and ribs.

But even drowning in his own discomfort, it’s impossible not to feel it when the air of the castle seethes and shifts as if drawn by an invisible current. Cross is on his feet and moving purely on instinct, hastily gathering up the crumpled pieces of his uniform.

_ What is it? _ Chara sounds confused, which means he didn’t understand what that powerful pull of magic signified

“Nightmare,” Cross says shortly, scrambling into his clothes. His phalanges are slippery with sweat, making him fumble with every clasp and button, but the ingrained habits of his training compel him to pull on his heavy jacket and even his cape. The layers feel hot and heavy on his tender bones but duty outweighs his discomfort.“There’s trouble.

The cloud of negativity that hangs over the castle is Nightmare’s first line of defence. He only draws on it when he’s preparing for a threat. These days he also prefers not to fight unless all of them are present for the greatest possible advantage, which means something unexpected has happened. 

Urgently, Cross thumps his fist against the door. “Dust? What’s going on?”

There’s no answer, and no sound of movement in the corridor. Dust is gone -- maybe has been for a while. Cross’s soul roils. His LV feels unusually close to the surface, sending his already raw instincts into overdrive. Unease and concern sharpen into an aggressive, territorial fury that someone would dare intrude on his ( _ nest _ ) home and threaten his ( _ mates _ ) team

_ You know your magic still isn’t working, right _ ? Chara reminds him, watching Cross’s quivering posture warily.  _ I don’t think we should- _

Cross isn’t listening. Even if his magic isn’t working, he’s had time to think about how to draw on Chara’s code without relying on his own power. This time, when he summons the sword, it comes easily to his hand, the blade burning red with Chara’s determination. He slices the door in half, and from the edges of the cut the entire frame begins disintegrating into reels of binary numbers and chips of smouldering wood.

_ I hate it when you ignore me _ , Chara mutters, but grudgingly trails in Cross’s wake. 

The corridor is vacant. There’s no sign of destruction other than the newly shattered door, but then the ambience of the castle shifts again like it’s drawing an anticipatory breath. Nightmare’s aura presses down on him, as encompassing as gravity. If Cross focuses, he can feel the epicentre of his negativity coming from the heart of the castle. The throne room, then. It’s a poor battleground for anyone trying to pick a fight with him, but perhaps Nightmare drew them there on purpose. 

The Boss is probably fine. It’s his castle, his AU. He’s surrounded by allies. He must be safe, but-

_ Protect, protect, protect _ , Cross’s instincts chant, a maddening echo in his skull, louder than the indistinct murmur of Chara’s voice trying to get his attention. 

With a low growl he tears open a code-riddled shortcut and vaults into the cavernous throne room. He almost stumbles, head swimming from the unexpected drain of leaning too hard on Chara’s powers instead of balancing it with his own magic, but even with his vision dappling with concerning black spots he immediately spots the unwelcome intruder.

“Error,” he spits, the blade of his sword sparking warningly along its edge. Error is standing before the dias of Nightmare’s throne, one foot resting impertinently on the steps like he means to approach. Nightmare himself is seated, his expression set in the droll combination of guarded interest and haughty arrogance that he often wears around Error, who is...not a teammate or even an ally, but occasionally acts alongside them if it happens to work in his interests. Cross has gone out of his way to avoid the unstable skeleton, still resentful of the time Error stole his soul and nearly killed him.

Error’s visits are sporadic, unannounced and usually kept as short as possible for everyone’s peace of mind. Mostly he drops in with information to share in exchange for favours, but even as an informant he’s still a wild card. He’s made no secret of the fact that he considers them all -- save Nightmare, whose being is tied to the foundation of the whole multiverse -- to be the same abominations he’s sworn to destroy...just at a later date, when it’s more convenient. None of the others consider him a very serious threat, but Cross has never been able to see him as anything but an enemy waiting to turn on them. 

“O-oh, it’s yOu,” Error sneers back, glancing disinterestedly over his shoulder. “WhAt do you w-want, aboMinAtion? Usually you’re tOo sCared to cOMe near ME.

It’s not the taunt that goads Cross -- the words hardly register over the screaming of his instincts. His focus is on the subtle flex of Error’s fingers, tugging at the strings wrapped around his phalanges. The threads are too fine for Cross to discern what they’re attached to, but the fact that he has them summoned at all is an implicit threat even if he’s simply using them to augment his poor vision. 

“Cross.” Nightmare’s call is soft but firm. Cross twitches, his ingrained obedience almost enough to divert him, but the potential danger Error represents demands his attention. He barely hears the exasperated reprimand. “You’re supposed to stay confined in your room-

Error’s fingers twitch. Whether it’s in response to the aggravation in Nightmare’s voice or just an accidental reflex, Cross doesn’t care. He lunges forward, sword arcing in a wide, reckless swing intended to drive Error away from Nightmare so Cross can plant himself firmly between them

Error’s splutter is gratifying, as is the way he nearly stumbles as he dodges back, face twisted in outrage and surprise. Cross doesn’t give him a moment to recover, rapidly closing the distance, slicing through the strings that try to block his way like a tangle of spiderwebs. 

Taking down Error is an eventuality Cross has long prepared for. The destroyer is powerful, no doubt, but he’s far less effective in close combat while Cross excels at it. He’s careful not to step on any of the fallen strings even after they’ve been cut, skipping between them like a dangerous game of hop-scotch as he relentlessly backs Error into the corner of the throne room, ruthlessly invading the protective space Error tries to keep around him.

“G-godDAmnit! NightMare, cAll off your guARd-dog!” Error snarls, his face twisted in disgust and alarm as Cross uses the flat of his blade to slam him back against one of the walls. Error’s body shudders and pixelates along the point of contact, fragments of angry code crackling incoherently in Cross’s vision. It’s not overtly damaging, he thinks, but it’s enough to disrupt any retaliatory magic Error might try to throw at him.

A heavy, ominous weight falls across his back. Even though the stifling heat of his clothes, it feels like the temperature of the room plummets to a dangerous chill. 

“Cross. What do you think you’re doing?”

The cold timbre of Nightmare’s voice sends a shudder down Cross’s spine, but he doesn’t dare divert his attention from Error for even a second. The destroyer is cursing and writhing, trying to shove Cross away without actually touching him which limits his effectiveness -- exactly as Cross intended. He’s pinned and off-balance, and though it’s not a retribution equal to having his soul stolen, Cross feels a feral satisfaction at finally getting to take the arrogant glitch down a peg even if he’s risking Nightmare’s displeasure to do so.

He can hear the sound of Nightmare’s footsteps approaching in slow, measured steps. The caution seems unwarranted considering Cross has the threat nearly subdued. “Error’s here on business. Let him go, Cross.”

“No,” Cross growls thickly, thoughtlessly, but even as he flinches from the realisation that he’s refusing Nightmare’s order his instincts are utterly convinced that he’s doing the right thing. Error isn’t one of THEM. he’s not safe. He’s a threat. Cross needs to get rid of him, or--

Or make sure he can’t leave. Nightmare’s always wanted to recruit Error, which Cross has never been in favour of, but with Error’s body squirming against him Cross finds himself reconsidering his stance. Error is powerful, unpredictable, but he could be brought to submit before Nightmare (before _ all of them _ ) then they would all be stronger for it. Safer. Cross just needs to show Error his place. He leans in hard, baring his fangs in a show of dominance. Error jerks back, nasal ridge crinkling in distaste.

“You sTink, abomNation, what are...you…?”

Sudden aghast realisation crosses Error’s face. He thrashes more violently, trying to shove Cross back. “Ugh! Get of! G-get aWay from me! Keep your F-Filthy heat-sCent to yourSelf!

Error may be taller, but Cross’s stance is unyielding. He presses forwards, forcing more pressure against Error, letting their bodies actually touch. Error makes a strangled sound, his form pixellating more violently. It sparks like electricity, a static prickling, but also clings and slithers over Cross’s clothes. The broken code pulls against him like a plea for help. It’s strangely saddening, watching it try to coax out fragments of Cross’s own code to fix itself only to have the stolen pieces indignantly break free to return to their origin. He doubts there’s anything his own limited powers could do to fix Error, but maybe he could soothe those jagged edges, find ways to make them feel good…

“Nightmare!” Error screeches, his sockets flickering like faulty monitors. Senseless code is streaming from his skull like a cloud of smoke, blotting out his vision, leaving him even more vulnerable. It’s perfect. All Cross has to do is lean in and-

He’s yanked abruptly backwards, a reprimanding tentacle wrapped firmly around his chest. The shock of it makes his sword slip from his fingers, and the moment it leaves his grip it evaporates into nothingness. He hisses in alarm at the loss of his weapon, but fortunately there’s no vengeful retaliation. Error is frozen eerily in place, emitting a gurgle of static and a high-pitched series of beeps. There’s a flickering bar hovering above his skull, slowly filling up by percentage increments.

Nightmare’s expression is full of glowering disappointment. He gives Cross a firm shake, rattling his skull. “I told you to leave him.”

“Hnnn,” Cross whines in objection. He dares to turn his gaze from Nightmare back towards Error, scrutinising him closely like he might be playing dead. His code fragments are snaking in confusion, like they’re trying to figure out where Cross has gone, but even as Cross tries to lurch back towards his prospective (mate) teammate, Nightmare secures him with a second tentacle and lifts him into the air. 

“Now I have to wait for him to reboot before we can finish,” Nightmare grumbles, carrying Cross away from Error. The sludge across his bones is oozing more intensely. Even if Nightmare’s voice is calm, his emotions are not. “I’m disappointed, Cross. That’s twice today you’ve disobeyed orders.

The tentacle squeezes tightly, but it’s the accompanying crush of power that drives the breath from Cross’s lungs. It’s like being plunged into icy water, shocking and sobering. He blinks rapidly, heat-muddled thoughts clearing to reveal the stark reality of the situation.

Error is going to be furious.

“I…” Cross jerks, trying to turn back to Error, though this time it’s only to ensure he’s not about to find himself dangling from a noose of strings or with his soul being torn from his chest a second time. Thankfully Error still seems to be stuck, the progress bar not even half-full. “Boss, I-”

“Quiet,” Nightmare snaps, and this time Cross obeys without question, head bowed in meek submission. 

He doesn’t fight as Nightmare drags him towards the throne room’s entryway, pausing before the doors and glaring meaningfully towards the shadows of the room. 

“And you three,” Nightmare barks, arms crossed over his sternum, “were too busy spectating to make yourselves useful, I see.”

There’s a blur of motion as Killer and Dust shortcut out from wherever they were hiding. Horror follows more sedately, slipping out from behind one of the ornate support pillars. None of them look particularly chastened by Nightmare’s accusation.

“Sorry, Boss,” Killer says with an unrepentant grin. “Kinda figured we’d just make things worse if we stepped in. You know how glitchy-boy gets about us abominations.”

Dust’s grin is manic with amusement. “‘Sides, it’s not like you couldn’t have stepped in a little quicker if you’d really wanted to.”

“Could have had a nice show if you hadn’t,” Horror offers, licking his teeth suggestively enough to make Cross suspect he’d been hoping for more than Error’s blood on the floor. He’s suddenly glad for the shield of his turtleneck hiding at least part of his flushing face from view.

“Error has information I need,” Nightmare tells them sternly. “It’s not going to be easy to negotiate with him after this setback. And which one of you was supposed to be watching Cross?”

Three blithe expressions of incomprehension stare back at him, like Nightmare’s question was spoken in a foreign language that none of them can understand. There’s clearly no intention to give up the guilty party, and Nightmare lets out an aggrieved sound, like the kind xGaster used to make when he was fighting off a migraine. 

“Never mind,” he says, thrusting Cross forward and unceremoniously dropping him in front of the trio. “Killer, you can help me with Error. Dust, Horror, take Cross back to his room.”

“Ha! Later, suckers,” Killer taunts with a cheeky wink at Dust and Horror. “Have fun babysitting.”

“Asshole,” Dust retorts without much venom. “Hope the glitch turns you into one of his creepy dolls.

While Horror shoulders open the door, Dust makes a curt gesture with his hand that wraps around Cross’s soul and turns it blue. It pulls like a tether, tugging him to follow along in Dust’s wake. Cross clearly isn’t trusted to behave, which isn’t entirely unwarranted. It feels like a walk of shame, thoroughly deserved, as he follows along behind them, held firmly at a distance.

It’s Dust who breaks the quiet, glancing back over his shoulder at Cross with a pointed sniff in his direction. “Error was right, though. You really stink, Cross.”

Cross flinches, chastened. His sense of smell has grown much more sensitive since the beginning of his heat, which has only made him more aware of the new potency of his own scent. It’s a musky, invasive odor, not exactly unpleasant but potent enough to be embarrassingly noticeable. 

“Sorry,” he murmurs, pulling his hood up and his coat around him as if it’ll help quell the scent. He can only assume that’s part of the reason Dust is holding him at a distance, but watching the two of them from beneath the ruff of his hood makes him realise it’s not exactly because the smell is off putting. Dust is holding himself stiffly, his spine uncharacteristically straight instead of its usual careless slouch, and Horror keeps twitching like he’s trying not to turn around and stare. Both of them are breathing shallowly, radiating the kind of tension that usually only proceeds a fight when they’re struggling to hold themselves back.

Cross is still pondering the implications of that when they finally reach the door to this room...or what’s left of it. Fragments of shattered wood lie scattered across the floor like a ruined jigsaw. Dust sourly nudges one of the segments with his shoe, and crumbles even further with a puff of sawdust. It doesn’t take a puzzle expert to determine there’s not enough pieces left to even attempt putting it back together. 

Horror sighs, picking absently at the crack on his skull. “This ain’t gonna work. I’ll put him in the guest wing. You better clean this up before the Boss sees it. You know how he feels about mess.”

“Why me?” Dust’s eyelights flare brightly with dangerous displeasure.

“You were the one on watch,” Horror says mildly. “‘Sides. Kinda looks like you need a minute.”

Dust stares back for a moment, uncomprehending, before following Horror’s gaze downward. There’s a subtle bulge beneath his shorts that might have been nearly unnoticeable if not for the bright flare of magic that glowed beneath the fabric like a poorly obscured ember. Cross stares as well, his body stilling with surprise and a mortifying fascination. His shorts aren’t the only thing glowing. His hands are too, flickers of red and blue crackling between his phalanges. Even his eye-lights seem brighter as he levels a sullen glare at Cross that lingers for a breathless moment before Dust abruptly turns away.

“Fuck off,” Dust says emphatically as he pulls his hood down further over his skull, but not quite fast enough to hide the warm flare across his cheekbones. Cross doesn’t think he’s ever seen Dust blush before. “Fine. I’ll handle it. Go put this asshole back in lockdown.”

With a snap of his fingers he dispels the hold on Cross’s soul and storms into the bedroom. Cross makes a low sound in his throat and instinctively moves to follow, only for Horror to catch him by the humerus.

“Nope, bad idea. How ‘bout you come with me instead.” Horror’s grip is unyielding, and Cross’s arm tingles but not in an uncomfortable way. It’s different from the static prickle of Error’s code; just the subtle resonance of Horror’s innate magic thrumming against his own. He craves it so badly he allows himself to be pulled along without putting up any resistance.

“Um…” There’s nothing soft or even particularly illicit about Horror’s grip, but Cross feels stupidly like an awkward teenager on their first date. They’re alone. Horror is touching him. His soul is having all sorts of feelings about this development, pounding wildly inside his ribcage. “Is he...okay?”

_ Heats are contagious, Dumbass _ , Dust had told him. Belatedly, Cross feels a deeper stab of guilt. Now that he’s learned how unpleasant heat can be, he certainly doesn’t wish it on anyone else.

“He’ll be fine,” Horror says with an unconcerned shrug. He pauses, thinking, then leans in and deliberately breaths more deeply in Cross’s space. He nods to himself. “Yep. You’re still in the first stage. Pretty safe for another day or two, I’d guess.”

So Dust hadn’t caught his heat, but he’d certainly looked...affected. That bright glow beneath his shorts is an image forever caught in Cross’s mind, and Cross hadn’t even gotten within five feet of him. “But...you’re…?

“Hm?” Horror follow’s Cross’s gaze to where his large, broad hand is curled around Cross’s arm, no hint of unusual brightness between his knuckles. His expression twists into something faintly bittersweet. “Nope. Monsters with high magic get hit harder by the heat scent. For me...well, ain’t much point if there’s not enough batter for the babybones.”

Years of starvation had left Horror’s magic reserves unusually low for a monster of his size. Even after considerable time to recover, he still relies on his axe instead of bone attacks, and though he’s fast on his feet he’s never used a shortcut. He faintly remembers Nightmare mentioning that Horror hasn’t had a heat in several years now, and Cross wonders faintly if that’s why he doesn’t feel quite so aggressively fixated by the need to get closer to him.

Though that doesn’t seem quite right, because even without the aggressive spark he’d felt from his magic pushing against Error’, surging with the need to dominate and overwhelm, there’s no shortage of (embarrassing, inappropriate) desire running through him. It simply feels calmer; like there’s no question that Horror will take care of him even though his imagination keeps purposefully blanking out on detailing exactly what that might entail. All Cross knows is that he feels enthralled, his focus on Horror so acute he barely even notices when they finally arrive at their destination.

There’s numerous areas of the Castle that Cross knows exist in theory though he’s never had reason to visit them. Supposedly there’s a garden somewhere outside the walls, and Killer swears up and down there’s a wine cellar somewhere down in the basement. The guest room has never been occupied since Cross arrived at the castle, though the heavy locks on the doors suggests not every guest has been a willing one. When Horror pushes open the door, however, the room inside is perfectly respectable, plainly furnished but understatedly luxurious. Nightmare takes a certain amount of pride in his domain, even the parts that rarely see use.

Horror gives it a frank once-over and seems to deign it acceptable. He casually manhandles Cross until he can push the smaller skeleton across the threshold. “Here we go. Try and stay put this time. Boss is already out of sorts having to revise his precious schedule. Might wanna stay on his good side, yeah?”

“Okay,” Cross repeats helplessly, feeling at a loss. He looks back at Horror, trying to untangle the conflicting impulses to obey that command whilst struggling with the sudden anxiety at being left on his own again. 

Horror’s stoic expression softens slightly. “If you’re good, I’ll bring you more of that stew later. You liked that, didn’t you?”

Cross’s breath catches. The way Horror’s voice lowered into a deep, almost sultry tumble makes his soul squeeze hard. His whole body gives a pleasant shiver of remembrance, his sockets lidding heavily at just the thought of that taste in his mouth again. Weakly, he whimpers, “Y-yes.”

Horror’s hand cups the side of his skull in a gentle pat, a gesture Cross would normally find condescending and intolerable, but instead his sockets flutter shut as he leans in hard to the offer of affection. “Heh. Good boy.”

By the time he registers that the contact has been withdrawn, the door has already closed in his face. Cross blinks rapidly, still reeling as the lock turns with a loud, significant clunk, leaving him locked in and alone once again

Or as alone as he ever is. Chara fades into view beside him, looking extremely disgruntled. _ I knew he put something in that stew. _

Cross leans against the door, trying to follow the quiet shuffle of Horror’s steps. Chara’s voice is as distant and unimportant as a buzzing mosquito. “Huh?”

Chara gives an emphatic sigh.  _ Nothing. Stop pining after the big oaf. You look like enough of an idiot already. _

Cross mutters a surly curse under his breath, but reluctantly pries himself away from the door, turning to survey his new, temporary lodgings. The room was almost the size of his own, not small by any means, but already the walls feel uncomfortably close. He stalks from one end of the room to the other, haphazardly tugging off the outer layers of his uniform as he does so. He carelessly discards each garment across the floor, then restlessly changes his mind, gathering them all up again and piling them into the corner. He stares at the pitiful pile, jittering anxiously. It’s not enough. He turns to the bed and begins aggressively yanking off its layers, stripping every sheet and pillow and adding it to his chosen corner. Dissatisfied with the arrangement, he gets down on his knees and starts shuffling it around to a more pleasing configuration.

Chara watches him for a silent, bemused minute before finally asking,  _ Why do you keep doing that? There’s nothing wrong with the bed _

Cross pauses in the middle of burrowing out a scoop-like indent amidst the blankets, confronted by the realisation that he didn’t really understand his actions either. It just feels right. Like sharpening his blades or practicing with his blasters; some necessary, preparatory step in expectation of...something. He’s not quite sure what.

It’s still not complete, though. He stares down apprehensively at the sheets and gravely informs Chara, “It’s not right.”

_ Uh. _ Chara already looks full of regret before asking,  _ What isn’t? _

Cross gestures frustratedly at everything, struggling to put the dissonant problem into words. He only manages to come up with, “It...smells wrong”

You smell wrong, Chara retorts snappily. At Cross’s resentful glare, the human makes a grandiose show of leaning down to sniff the blankets. Cross feels his own nasal ridge itch as Chara borrows his senses.  _ It smells fine? I mean, it smells like that awful lilac detergent Dust keeps picking up on supply runs, but.. _

Cross shakes his head sharply. It’s not the detergent that’s the problem -- he’s grown used to the oddness of all his laundry smelling incongruous of cheerfully floral sweetness. Rather, it’s the scents that are missing that’s the problem.

Though there had been a very deliberate (borderline insulting) lack of fanfare when Nightmare has brought him to the castle, at some point or another he’d been dropped in on by the others with an assortment of dubious cast-offs that also somehow qualified as ‘moving in’ presents. Second hand clothing from Killer, that had been delivered along with some derisive remarks about the impracticality of Cross’s cape. Horror’s gift had been an extremely obnoxious alarm clock and the stern reminder that breakfast was not to be missed or there would be extra kitchen duty for a week. Dust had delivered a bunch of candles with the dry warning that the electricity in the castle tended to fail when Nightmare was in a bad mood...which had proven true just a few days later, and also shown that the odd holder that had come with the candles projected the outline of stars on Cross’s walls when lit up from the inside.

Even Nightmare had brought in a stack of books. Not the standard, printed kind found in stores, but hand-written accounts of various multiverse worlds and events that he felt Cross should be aware of. They were painful to read, but precious because after handling some of Nightmare’s reports and becoming familiar with his handwriting Cross eventually realised the Boss had written those books himself

As much as Cross tried to keep the others out of his personal space, it had still accrued the comforting, intermingling essence of the others that he’s long taken for granted. Without it he feels bereft. The guest room smells barren, unfamiliar and unsafe. Beneath the heavy weight of Nightmare’s admonishment and the distracted itch of his heat, there’s a new, unsettling anxiety settling into his soul that he doesn’t like one bit. 

_ You’re thinking of doing something stupid again _ , Chara observes flatly.  _ You really gonna get on everyone’s bad side? _

Cross bristles. “They won’t find out.” 

They won’t; Cross won’t even be breaking his promise to Horror, exactly. He doesn’t need to leave...not when Chara’s powers can simply cut a hole through to other parts of the castle, connecting distant spaces even better than a shortcut can. He’s already done it once today, carving through reality to get to the throne room faster than he could blink. He can access anyplace he needs to as long as he’s been there at least once before

Experimentally, he calls up one of Chara’s knives - just one of the small ones, no longer than his forearm. He doesn’t need a whole doorway, just enough of a gap to reach through. He concentrates for a moment then slashes the air, tearing open a jagged rift that lets him peer through to the inside of the kitchen pantry. Pleased with himself, he sticks his arm through the portal and snatches the end of the apron he can see hanging from a hook on the shelves. WIth a quick jerk he flicks it free and drags it to his chest, gleefully inhaling the layers of Horror’s scent that have built up on the garment over time.

_ You know, when I said I’d let you borrow my powers, this isn’t what you were supposed to use them for _ , Chara says plaintively, looking distinctly unimpressed by this development. 

Cross raids Dust’s room next. Another sharp tear brings him to the other skeleton’s unkempt bedroom, which is thankfully unoccupied. Either he finished taking care of his earlier problem, or perhaps he’d decided to use Cross’s room instead of his own. Cross falters over that thought, almost losing himself to distraction before shaking it off and returning to the task at hand. There’s plenty of discarded clothing strewn across Dust’s floor, including a truly staggering number of stray socks. Cross reaches furtively through his tiny portal and manages to snag the sleeve of a hoodie, dragging it eagerly into his lap to join Horror’s apron.

_ When your heat is over, I’m gonna remind you about this _ , Chara promises with what Cross feels is an unnecessary amount of vindictive exasperation.  _ Next time I get control of your body I’m gonna tell everyone. _

Cross ignores his, stitching the portal shut with a hasty patch of code, and creating a new one down to Killer’s room. His room is, surprisingly, much neater than Dust’s. Even though he’s been with Nightmare the longest, his room looks almost empty, devoid of all but the barest essentials. Aside from the knives strewn across the dresser, there’s nothing personal left out in sight. Cross isn’t quite brave enough to go rifling through Killer’s drawers (god knows what’s hidden in them) but the extravagant surplus of pillows Nightmare encourages on every bed means that Killer shouldn’t readily notice that one of them is missing. Cross has to lean his upper body through the narrow portal to reach the bed, feeling disconcerting unmoored as he strains across the distance, but finally he manages to snag the corner of a pillow case and hauls it to safety. 

For a brief moment, he wonders if he dares plunder Nightmare’s room for another token of comfort, but as much as he wants it he can’t shake the unassailable certainty that Nightmare would  _ know _ no matter how careful or insignificant his theft. He’ll have to settle for the faint scent of ozone and charred apple clinging to his own clothing after being ensconced in the boss’s tentacles. Pleased with his work, he sets about buying the apron and hoodie beneath the upper layers of his nest, hiding the distinctive item from sight. Killer’s pillow is granted a place of honor near the top, its plain casing indistinguishable from the others aside from the distinctive scent of cold metal and tar that clings to it.

_ Uh huh. The perfect crime _ , says Chara with a roll of his eyes. 

Cross ignores him, curling up gratefully amidst the soothing smells of his (mates) (home) idiot teammates as the unsettled knot in his chest finally starts to unwind. He’s safe. They’re all safe. For now, that’s enough to make the restless gnawing of heat and instincts subside. 

  
  
  


**Notes for the Chapter:**

> Assorted headcanon extras:
> 
> \- Dust's 'bro' is actually the one with very strong opinions about laundry detergent.  
> \- One of the benefits of 'sharing' magic with a heat-afflicted monster (sexually or via the aforementioned home remedy method') is that they become a lot more receptive and suggestible to the donor. It basically feels like a consummated bond, and therefore they feel safer, more settled. c: Horror knew that was a likely outcome when he did it, but don't worry. He trusts himself to keep a clear head and not ask Cross for anything he wouldn't want to give.


	6. Chapter 6

Cross is no stranger to pain and discomfort. Years of training as a royal guard means he’s familiar with all manner of hurt. Between brutal training and regular field work, he’s experienced cruises, cuts, cracked bones, magic ailments and even burns, from the few occasions he’d sparred with Prince Asriel. There’s several monster types with fire magic, and even humans have learned to weaponise the element either through modern weaponry or just the convenient application of burning torches.

Skeletons aren’t as vulnerable to heat as monsters with flesh, but it’s still painful. A hot enough fire causes half-melted blisters on his body in a series of unsightly pockmarks, or can boil the marrow until the bone blackens and cracks apart. It’s nasty, but usually the worse the injury, the less it hurts as the nerves simply scorch away.

This heat, however, doesn’t seem to reach any sensible limit. The burn inside him is constant and unignorable, becoming more acute with every passing hour. There’s a growing pressure too, weighing heavy in his soul that makes every part of him ache. It feels like the pent-up tension he gets when he hasn’t trained in a couple of days -- a discomfort which only grew more frequent and intense after gaining LOVE. His magic is stronger now, more volatile, and the build-up leaves him feeling irritable and tense until he’s able to vent it.

Only now he can’t. Not just because he’s forbidden from leaving the room, but his body is stubbornly holding onto all the excess. He’s already tried summoning a few bone attacks in the air, but not he can’t call up even the simplest of constructs he first learned as a babybones. He’s starting to realise it must be some facet of the heat itself, storing up all his magic as if he’s preparing for the creation of a new soul. 

xGaster was never a particularly attentive guardian, but he was stringent about delivering a well-rounded education. In addition to the standard schooling on monster physiology, Cross vaguely remembers learning how the number of skeletons in the population had fallen into decline. Compared to other monster types, the fertility rates among skeletons were quite low simply because of the high energy requirement for conception. A new babybones required a lot of magic to form and hold their body together, and they were especially fragile and delicate in the early stages of formation. 

Creating a child also takes a lot of intent, and though Cross knows he doesn’t want one yet he desperately wants to release all this energy. He’s starting not to care how that happens, the dwindling rational corner of his mind is starting to realise why Nightmare made sure to post guards. Without the deterrent, Cross isn’t sure he could convince himself to stay where he is, not even with the reassuring scents of his teammates surrounding him.

 _You should eat something_ , Chara says from where he’s sitting just outside the circumference of the nest. The first time he’d tried to come closer, Cross had given a savage snarl of warning that had taken them both aback with its bestial cadence. Chara hadn’t tried again, though he’d insisted on remaining corporeal since just waiting inside Cross’s soul was unbearably boring. _You haven’t had anything since yesterday._

Cross has no idea what time it is, or even how long it’s been since his heat started. Two days? More? It’s all blurring together. Every hour is an unbearable, overheated eternity, but the thought of putting food -- more energy -- into his body is utterly nauseating.

Unless it was Horror’s stew. He’d promised to bring Cross more. 

( _His hand was cool on Cross’s face. Good boy, he’d said, and Cross had wanted to lean into that steadying touch and prove just how_ **_good_ ** _he could be…_ )

Had he done that already? Cross honestly can’t remember. Even if he has, surely Cross has been good enough to deserve more. Covert acts of thievery aside, he’s remained in the room as ordered, curled up with Killer’s pillow clutched tightly to his chest. As plush and comfortable as it is, the pillow’s not a good substitute for another body. It’s too soft, with too much give to be mistaken for bone, but now it smells like both of them. Their mingled scent is soothing enough that he’s managed to snatch a few short, shallow hours of sleep between longer periods of heated suffering. 

With immense effort, he uncurls from his tight ball of misery and sits up. There’s an unpleasant pressure under his frontal lobe, like the beginnings of a headache. His eyes ache, fizzing in his sockets with oversaturated magic, making the room blur fuzzily around him. For a moment, he’s hesitant to leave the safety of his nest, his skewed vision making him uneasy, but listening carefully he can hear the soft exchange of voices beyond the door. In particular, he can hear Horror’s gentle, rumbling baritone which spurs him into action.

His balance is nearly as poor as his sight, but leaning heavily on the wall he manages to drag himself upright. The pressure behind his eyes seems to slosh around like his skull is full of water. He hisses, giving his head a hard shake like he might if he’d been submerged, and oddly enough there’s an audible pop of sound and the knot of tension loosens so abruptly that the lack of it feels nearly euphorically pleasant. A rush of wetness slides down his face, like tears of relief, and he absently wipes at his cheeks. 

_Uh. That’s new._ Chara is staring at him, looking unsettled. _Are you...bleeding from your eyes?_

Cross glances down at his fingers. They’re smeared with purple, but even up close his gaze won’t seem to focus properly for him to make out more than the contrast of color. Without much consideration he licks at it instead. There’s a strong, acrid tang, but it’s not blood. Just his magic, thick and oddly coagulated as it leaks intermittently from his sockets. It’s a little messy, but not much more so than the sweat dripping down his spine, so he ignores it in favour of making his halting, wobbly way towards the sound of voices. 

_Hey, be more careful with our body, idiot,_ Chara growls, pulling uselessly at Cross’s arm like he wants to drag the skeleton back into the nest. _You’re not the only one in trouble if something goes wrong._

Even though Chara has no tangible presence, Cross hitches his shoulder to shake the human off. He doesn’t care about Chara’s complaints, he just wants Horror. Beneath the oozing coat of magic, his cheek still tingles faintly with the memory of coarse phalanges cupping his jaw (good boy) and as he gets closer the pleasing rumble of Horror’s voice sets his soul resonating like a tuning fork. 

“-was supposed to be a cake walk,” Horror is saying. “What went wrong?

“No idea,” Dust replies. “But Boss said we’ll need to pull double shifts while Killer’s healing up.”

Cross pauses, holding still and silent as he leans forward, listening intently.

Horror sighs as if greatly put upon, but there’s a gruff concern in his tone when he asks, “How bad is it?”

“Well the infirmary looks like a murder scene, but you know what he’s like. Says he’ll be back in action in a day or two. Not sure he ran that past the Boss, but-”

The soft, yearning resonance in his soul turns into a tight, anxious pounding. Killer is injured...how can Killer be injured? These days Nightmare always sends them out in pairs for greater effectiveness and for backup in case the Star Sanses show up. Killer is his partner, he shouldn’t have been sent alone.

Unless it was a mission too important to wait, and not one Dust and Horror could handle. Each team has their own strengths. Dust and Horror are their powerhouses. Horror’s raw physical strength and Dust’s bottomless magic reserves make them an incredibly destructive duo, but Horror can't handle long missions and needs to frequently break for food, and Dust is high-strung and has difficulty restraining his need for violence. Neither of them are suited to tasks that require stealth or negotiation. Those are Killer’s specialty, and Cross’s role is to watch his back and provide a quick exit if things go poorly. 

_He’s fine,_ Chara says, interrupting Cross’s spiralling train of thought. Of course, he can hear everything Cross does. _That bastard’s practically indestructible. Why are you even worried?_

The same overpowering sense of wrongness he felt before properly adorning his nest comes back to him. This isn’t right, Killer needs to be safe, everyone needs to be safe. The knowledge that he’s not -- that he could be bleeding, hurt, vulnerable -- makes the burn of the heat feel dull next to the twisting dread in his soul. He can’t stand it. He needs to check-!

 _Oh no you don’t_ , Chara growls when Cross tries to reach for his powers again. The hilt of a knife wavers in his palm, glitching and struggling to take form. Chara’s fighting him for control, trying to prevent him from accessing their code abilities. _Damnit, Cross-!_

Their soul is shared, but the body belongs to Cross which has always given him the advantage in remaining the dominant personality. Chara’s resistance is short-lived and futile, and with a snarling sound of defeat Chara is forced to let him have the knife. Cross holds it so tightly his knuckles ache, hand trembling.

 _You’re being stupid again_ , Chara warns darkly. _You’re going to screw things up. This always happens when you don’t listen to me. You never stop to think!_

There’s no time to think when Killer is injured -- when Killer _needs_ him. Recklessly, Cross tears open a portal, aiming blindly for the infirmary. Some small corner of his mind, the part that faintly remembers Horror's instruction (good boy) tries to believe that all he’ll do is look. He’ll just check, just to make sure that Killer is really alright, that one glance is all he’ll need to reassure the sudden wild distress in his soul, and then he’ll be satisfied.

The thick smell of blood and dust spills out of the portal, like he’s opened a wound in the air itself. Blind panic takes him, and without hesitation he stumbles through the gap, looking anxiously around. 

“Killer?”

There's a jerk of motion on the bed as Killer sits up. Cross’s blurry vision can’t make out the full definition of his features, but the dark pits of his sockets look round; surprised. No doubt he’s grinning to try and hide the pained wince in his motion as he straightens his spine.

“Hey, Criss-cross,” Killer says smoothly. “You, uh...pretty sure you’re not meant to be here.”

The infirmary doesn’t look as bad as Dust described, though it’s wholly likely that if Nightmare has been here, he meticulously cleaned up any trace of mess. He often seems unable to help himself. Whenever he visits someone in the infirmary, his tentacles all set to work seemingly without his conscious direction, always clearing and sterilising every surface like he can’t stand to see them utilised for their intended purpose. The air smells potently of bleach, but it’s not enough to cover metallic undertones of dust and marrow.

“You’re hurt.” The thought consumes him, jarring and urgent. The unsettling smell of fresh blood draws him closer, moving more steadily on his feet now that his body is coiled tight against the possibility of threats. Killer watches him with the unblinking stare, gaze darting uneasily towards the glowing knife in Cross’s hand. He immediately drops it, letting it disintegrate back into formless code. He doesn’t want to scare (his mate) Killer. He just wants to help.

“You’re not looking so good yourself,” Killer tells him frankly. For a moment, Cross blinks uncomprehendingly until Killer makes a vague gesture at his face. Cross reaches up to his own, wiping away more of the seeping residue. Trying to blink it out of his eyes just makes it stick unpleasantly to the rims of his sockets, but it’s only a minor distraction.

“S’fine,” Cross assures him, voice rough. If the magic loss is affecting him in any way, he can’t feel it through the frenetic buzzing in his bones and the anxious thump in his soul.

“Okay. Sure. I’m fine too. Boss patched me up, see?” Killer lifts his arm, which has been tucked oddly against his chest. Now that he’s closer, Cross can see it’s bound in a cast and resting on a sling around his neck. He’s shirtless, and Cross can see a mottled smattering of bruises across his ribs along the same side like he’s been hit by something large and hard. The bareness of his bones makes him look smaller than usual, highlighting the narrow curves of his ribs and the delicacy of his collarbones. Ignoring the discomforting intensity of Cross’s stare, Killer boldly continues, “Speaking of the boss, let’s get you back before he-”

As Killer tries to get up, Cross simply pushes him back down on the mattress, and then straddles him for good measure. His arms curl protectectively over his (mate) partner as he leans in, inhaling deeply. The smell from Killer’s body is so much more potent than from the pillow Cross stole, but the vibrant metallic tang is now tainted with blood. Cross’s nose can pick up the faint astringence of antiseptic as well as the burnt-sweet musk of Nightmare. There’s also a new, foreign smell; an unpleasant chemical bitterness that reminds him of paint...

Ink, he realises. It’s Ink’s smell; Ink who hurt Killer and branded his body with these ugly, unwanted marks. Fury rises like a hot bile in his throat. There’s a sizzling hiss around his sockets, like his magic is boiling over in a fresh tide of outrage.

Killer is saying something to him, but the sounds are just meaningless mouth noises; irrelevant. Gripping him firmly by the back of the neck, Cross drags him closer and presses their mouths firmly together to make the noises stop. When Killer’s jaw goes still, teeth parting as he draws in a sharp breath, Cross deepens the kiss with a hungry growl, impressing it with a burst of powerful, possessive intent. 

_Hush. Mine._

Cross pushes closer, trying to connect them along as many points of contact as possible, and the resistance in Killer’s spine slowly gives way, allowing Cross to pin him back against the mattress. He’s careful not to let any of his weight press down on the breaks or bruises, having Killer under him, protected makes a purr rattle in Cross’s chest like the rumble of an earthquake.

Killer’s good arm is clenched tightly around Cross’s shoulder, almost bruisingly tight, but the thrill of bare bone-on-bone contact overrides the minor ache. His arm is rigid, like he’s not quite sure if he should be pushing Cross away or dragging him closer, and his breath is coming in short, shallow gasps like he’s trying not to inhale too deeply. His ribs are probably troubling him, Cross thinks with a small frown of distress. With a last, affectionate lick and a reassuring nuzzle against Killer’s teeth, he turns his attention towards the injuries

The red tint of Killer’s magic buzzes angrily around them, making them look hot and painful. Interspersed among the bruises are tiny cracks along the lattice of his ribs. They’re shallow, not deep enough to reach the marrow, but Cross finds them infuriating nonetheless, knowing who caused them. His vision crackles, eyelights sparking with furious heat and a fresh gush of magic that falls from his sockets and splatters down onto Killer’s ribs.

The sight of his magic smeared over Killer’s bones gives Cross a wonderful idea.

Healing has never been Cross’s strong suit, and his ability for it has only gotten weaker and more inconsistent since gaining LV. He can’t address Killer’s injuries in the traditional sense, no matter how much he wants to, but right now he’s positively overflowing with excess magic. In place of proper technique and natural ability, he can make up for it with sincere intent and unrestrained power

The spill of magic didn’t fall quite where it’s needed and he doesn’t trust his shaky hands not to cause further harm. After a moment of consideration, he realises the best course of action is to lean down and scoop up the residue with his tongue, keeping the pressure light and careful as he redeposits the gluey plaque of magic across one of the cracks and gently laves it into place.

Killer’s body is perfectly still, but there’s an unfamiliar catch in his voice when he breathes out a strangled, “F-fuck…”

Cross makes a wordless soothing sound. He knows it must hurt, but he’s trying to fix it. When the crack is filled with glowing purple, tiny flecks of light shimmering in place of the dark shadow of the split, he moves onto another. A thicker application probably means more effectiveness, so he scrubs his face down the unwounded plane of Killer’s sternum, dislodging more magic for him to work with whilst simultaneously satisfying the dark, feral need to ensure this mistake won’t happen again.

(The next time Ink sees Killer, he’ll know. He’ll know Killer belongs to Cross. He’ll know that if he tries to bring harm to Cross’s mate, Cross will _come for him_ and _tear him apart_ and _make him pay_ . He won’t dare spread his filthy smell and his unwanted marks all over someone that belongs to _Cross_.)

Killer is wriggling now, like a misbehaving kitten enduring a bath, murmuring something that sounds pleasingly like Cross’s name. Cross just shifts his weight to pin him more effectively, undeterred as he tries to urge more soothing relief into every swipe of his tongue. He’s almost done with Killer’s ribs now, and he’s trying to figure out how to address the injuries under the cast. It’s one of the thick, magic-reinforced casings designed to hold the bone in place while it heals, extending all the way from Killer’s knuckles to the upper cleft of his humerus. The break beneath must be a more serious one. Cross wants to see it, wants to stroke and salve it with his tongue and his magic, but destroying the brace might jar things out of alignment. He noses along its length, trusting his tactile senses rather than his failing sight to try and determine if there’s any obvious weak point to unravel it.

“Don’t,” Killer says, soft but sharp. It’s the first clear objection Cross has heard from him, and he backs off immediately, blinking down with concern. Killer takes in his expression and gives a ragged sigh. “Now, look, you really need to-”

He makes the mistake of shifting the grip of his good arm from Cross’s shoulder to his waist, trying to find better leverage to push back against him, but the moment Killer’s fingers brush against Cross’s illiac crest he gives a jolt of surprise that makes both of them hiss at the sudden, unexpected friction. Cross is straddling Killer’s hips, and the thin fabric of their respective shorts does nothing to obscure the burning heat of the bones beneath. Cross’s pelvis is still alight and tender, his pelvic cradle full of simmering magic that feels like it’s been ready to boil over for days. The brief grind of Killer’s pubic crest against his own is excruciatingly good. Even better is the hint of cushioning softness that’s starting to grow more solid and prominent at the crux of Killer’s legs, magic swelling, solidifying, taking on a shape to match the sudden ignition of arousal between them. 

“Fuck,” Killer says again, weakly, but Cross feels positively delighted at the realisation that even if he can’t help with Killer’s arm there’s something else he can do. Testingly, he grinds down again and is rewarded with a strangled, bitten-off sound that makes the tone of his purr drop to a lower, more gratified pitch. He can make Killer feel good. Cross will help him forget his pain, forget about Ink, will bathe him in magic not just over his bones but inside him, claiming him utterly. He reaches down to peel back the waistband of Killer’s shorts when the wall of the infirmary suddenly bubbles and turns back like it’s been scorched from the other side. A moment later, it condenses into a wet portal of shadows that hastily gives way before the small but formidable figure at its centre. Nightmare looks riled, his tentacles flaring around him like snakes preparing to strike. He looks every inch the indomitable King of Negativity, and his gaze settles on Cross with slitted displeasure.

“Cross.”

The thread of warning in his voice feels incongruous when Cross only feels eager relief at the sight of him. It’s like a piece of a jigsaw puzzle falling into place, something lost returned to its rightful owner. Nightmare’s arrival makes the situation even better. Now they can both take care of Killer -- keep him protected and comfortable.

(And pleasured. Cross’s face burns pleasantly at the thought of Killer’s frantic whimpers slipping through his teeth as Nightmare’s tentacles envelop them both. Imagines the messy tangle of scrabbling limbs and slippery tendrils beautifully entwined.)

Killer’s arm squirms out from under Cross, waving frantically. “Sup, Boss. Little help…?”

Nightmare’s glare sharpens further. The lingering traces of Ink’s invasive chemical smell are probably just as upsetting to him as they are to Cross. He’s still purring too intensely to be able to articulate proper words, but he offers a warbling trill of understanding, trying to coax Nightmare to come closer so Cross can comfort him more easily.

The mounting aggravation is abruptly snuffed behind a blank, unreadable expression before twisting into something more exasperated than annoyed. Nightmare has that pinched expression like he’s fighting off another headache, but he scrubs it from his face with a tentacle and makes a pointed beckoning gesture. “Cross, come here.”

Cross makes a short, reluctant whine. Getting up means leaving Killer unprotected (untouched, unclaimed), going against the urging of his instincts to stay exactly where he is.

“Cross,” Nightmare tries again, and there’s a subtle shift in his body language. His tentacles withdraw, their angry movements turning to sinuous coils. His tone is almost sultry, sweet and compelling. “Killer can’t handle you right now. Why don’t you come to me?”

His tentacles ripple with a hypnotising grace, twining around each other in a way that Cross never imagined they could. Their movements are an obscene glide of slippery enticement, and with only a brief hesitation he crawls carefully off Killer and stumbles towards the dance of roiling limbs. 

“That’s right,” Nightmare murmurs. “Come to me.”

Cross reaches out with eager arms, but the moment he gets close enough the tentacles pounce on him, wrapping him up in a firm, tight coil that pins his arms to his sides. The sudden surge of movement should have felt dangerous, but it’s Nightmare. ( _Mate_.) Cross feels perfectly safe, just faintly frustrated at his inability to touch back like he wants to.

Killer struggles to prop himself up on an elbow, and though his face is composed, the state of his bones looks utterly debauched; smeared with bright streaks of purple and hazed at the joints with flickering crimson. His white shorts do nothing to hide the ember glow between his legs. “Thanks.”

Nightmare flicks a quick, assessing glance in his direction before turning his full attention back on Cross. He folds his arms, sighing deeply. “I should have suspected after your last escape that there was something we were overlooking. Your magic should be inhibited by the heat, but it seems I should have taken more precautions against your other abilities. And this…?”

One of his tentacles swipes through the excess of magic on Cross’s face, lifting it for examination. There’s no deliberate sensuality in the gesture, but Cross shivers under the touch. He can’t lift his arms, but he’s close enough to turn his face towards the soft appendage and lap at its wriggling tip. Nightmare makes a distracted, impatient sound but doesn’t pull it out of his reach.

“You’ve let your magic build up too far,” Nightmare scolds. “Have you not been taking care of yourself?”

Cross is suckling happily, thoroughly distracted. He only shivers a little when Nightmare pulls aside his shorts and peers frankly down into his pelvis. Nightmare gives an agitated huff. “Nothing formed? You haven’t addressed the problem at all?”

“Happens sometimes,” Killer offers, having carefully eased up into a proper sitting position. “‘Specially for a first heat, if there’s no partner to settle the instincts.”

“I’m aware,” Nightmare says curtly. “I’ve done extensive research on the subject for the sake of you idiots. I also understand the dangers involved, and I’m not going to lose a subordinate over such a ridiculous biological compulsion.

The tentacles around Cross shift their hold so a pair of tendrils can slide seductively down the length of his ribs, the delicate tips petting encouraging whorls along the slats of bone.

“Cross. Give me your soul.”

Cross’s eyelights have blown wide, soft and diffused with hopeful need. He arches readily into the touch, waning nothing more than to surrender to that command. Faintly, he feels a twinge of worry at the possibility of a souling -- something they haven’t even discussed -- before remembering the medicinal pill Nightmare already demanded he take. If he’s right, it’s the same thing Killer mentioned, a pill to prevent any unwanted pregnancies, allowing a monster to enjoy their heat free of consequence. This is nothing more than an expression of pleasure and intimacy, and eagerly his soul bursts out of his chest and into Nightmare’s waiting grasp. 

His soul is so bright it casts the rest of the room in a stark contrast of glare and shadows. It’s swollen too, the pale monster half engorged and dripping, streaked with the same thick purple ooze that’s been dripping from his eye. Nightmare handles it carefully, barely touching the edges as he guides it closer to his chest and squints into its depths.

His blatant inspection makes Cross feel an embarrassing wave of conflicted arousal. His soul is too strange to meet the typical standards of aesthetic pleasingness. The mismatched halves look unnatural, the human side too dense and disquieting, and his own side bearing the worn patches of LV hardening and now its drenched coating of purple. For a moment, he worries that it's simply too ugly for Nightmare to want to touch, but the guardian must catch the poorly hidden flinch of shame. With a firm motion he stokes both thumbs down the construct in a smooth, confident caresse. 

The pressure borders on too much, excruciatingly good, and Cross throws his head back with a tight wail, thrashing helplessly. His soul sparks, and in the flares of light he catches both the cyan slit of Nightmare’s eye boring into him, and Killer’s sockets fixed on him with their unnerving, empty focus. Their nearness makes him want to reach out, to grab hold of an anchor to help bear through the intensity, but Nightmare keeps him firmly trapped and the constrictive embrace of his tentacles is a gratifying pressure on his bones, cool and relieving against his heat.

He wants to do more, to give back, but he’s forced to writhe in place as Nightmare’s touch ravages him in a breathless squeeze of hard, slick demand. It’s unrelenting, brutally fast, and it feels like the collision of a comet when Cross feels the pressure in his soul tighten to an unbearable level that bursts out in a rapturous release of light and raw magic.

It’s not quite the same as a physical climax -- the peak too desperate and fast for his body to keep pace with it -- but the near-painful weight lodged inside his soul feels slightly lighter, and his mind feels blissfully blank, whited-out with endorphins and the dizzy, adrenalised high of violent magical loss. Nightmare’s hold is the only thing holding him upright. Cross is fully dazed, incoherent, reeling with giddy relief.

Nightmare’s hands and sleeves are fully drenched in lewd splatters of purple, with more streaks having splashed back onto his face, but he bears it with surprising dignity as he maintains possession of Cross’s soul. He keeps it caged between his fingers despite the magnetised pull that tries to guide it back towards Cross’s chest. Cross makes a faint, inquisitive sound, sluggish and unfocused, that Nightmare answers with a sigh.

“This part may be slightly unpleasant,” he warns, delicately tracing the jagged line that splits the lobes of Cross’s soul. A thin trail of smoky darkness follows his finger like a smear of charcoal, imprinting a firm line. “But we can’t keep having you running loose.”

 _Hey, wait!_ Chara objects loudly, suddenly present and close, flailing urgently at Nightmare. _What are you doing to our soul?_

There’s no way for Chara to make himself heard without taking possession of Cross’s body, but Nightmare must feel the sudden surge of conflicting emotions. 

“Human,” Nightmare says, and across the room Killer goes tense, his broken arm twitching like he wants to reach for a knife. “Since you appear unable to restrict Cross’s access to your abilities, I’m creating a temporary barrier between your souls. I’ll refrain from strengthening it unnecessarily. Don’t try to break it, or I’ll be forced to replace it with a much more unpleasant restriction, and I may reconsider whether it’s worth releasing you once Cross’s heat has passed.”

 _T-this isn’t even my fault!_ Chara squawks in outrage. _Cross is the idiot with the stupid heat! Why do I have to be the one locked away._

The corner of Nightmare’s mouth twitches, the way it often does when he’s appreciatively sampling someone’s negative emotions. “Resent me if you must. You belong to me as much as Cross does, and this is for both your benefit.”

The dark smear condenses into a thin, jagged line that pinches tight, like it’s a band around his soul. Cross chokes on a breath, faintly aware of a sharper pain beneath the suffusing numbness of the afterglow. He claws briefly at his chest, but the edges of his vision are already going dark, his thoughts nothing more than sparks of broken, fragmented impulses scattering into senselessness.

He goes limp, not quite unconscious, but not coherent either. Cross’s sockets have slipped closed, and refuse to reopen, only fluttering faintly at his attempt. He distantly feels his body being lifted and arranged, settled properly into Nightmare’s arms, his skull resting heavily on the guardian’s shoulder. Only once he’s secure does Nightmare turn back to Killer.

“Did he hurt you?”

There’s a shuffle of movement, Killer resettling back on the bed. “Nope.”

There’s a skeptical pause, almost painfully poignant, and it’s Killer who caves first, adding, “Really. He seemed a lot more interested in fucking than fighting. Was real gentle, even.”

“Gentle,” Nightmare repeats, faintly incredulous. There’s a stiff pause before he adds with more assertion, “I’ll call Dust to take another look at your arm. He can help you to your room since this one will be in need of...refreshing.”

Killer gives an amused cackle. “That’s one way of saying it smells like a Lust-verse brothel in here. Our boy was real pent up, huh. He gonna be okay?”

There’s no particular fervor or worry in the question, but dimly Cross feels a faint sense of fondness wash over him. He lets out a soft breath, his face pressed into the crook of Nightmare’s neck.

“Of course,” Nightmare says with unassailable confidence. “I intend to make sure of it.”

An icy grip crawls over Cross’s body like he’s slipping underwater -- the familiar sensation of being pulled through one of Nightmare’s portals. He doesn’t even make it fully across the boundary before he’s thoroughly asleep, feeling safe and satisfied in Nightmare’s arms.


End file.
